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                <div class="autogen_class_views_documents_fourgen_toolbar" id="autogen_id_538574521"><div style="position: fixed; bottom: -35px; top: auto;" apturenohighlight="true" id="toolbar"><div id="toolbar_left_side"><div class="" id="scrubber"><div class="no_notches" id="all_track"><div style="width: 0px;" id="left_track"></div></div><div id="track"><div style="left: 0px;" class="selected" id="handle"><div href="#" id="handle_inner" onclick="return false;" ondrag="return false;"><div id="page_num" style="display: none;">1</div></div></div></div></div><div class="section controls"><div class="paging_controls"><div class="tooltip_wrapper" id="page_control_top_tooltip_wrapper"><div class="tooltip" id="page_control_top_tooltip" style="display: none; left: -1.5px; top: -7px;"><span class="inner" style="font-size: 11px; color: #ffffff;"><nobr>First Page</nobr></span><div style="" class="tooltip_tail"></div></div><a class="ctl_button to_top" id="page_control_top"></a></div><div class="tooltip_wrapper" id="page_control_up_tooltip_wrapper"><div class="tooltip" id="page_control_up_tooltip" style="display: none; left: 18px; top: -7px;"><span class="inner" style="font-size: 11px; color: #ffffff;"><nobr>Previous Page</nobr></span><div style="" class="tooltip_tail"></div></div><a class="ctl_button page_up" id="page_control_up"></a></div><div class="tooltip_wrapper" id="page_control_down_tooltip_wrapper"><div class="tooltip" id="page_control_down_tooltip" style="display: none; left: 58px; top: -7px;"><span class="inner" style="font-size: 11px; color: #ffffff;"><nobr>Next Page</nobr></span><div style="" class="tooltip_tail"></div></div><a class="ctl_button page_down" id="page_control_down"></a></div><div class="pages"><input value="1" class="current_page" id="current_page" type="text"><span>&nbsp; / &nbsp;</span><span class="max_page notranslate">57</span></div></div><div class="sectionlist"><div class="tooltip_wrapper" id="toolbar_sectionlist_tooltip_wrapper"><div class="tooltip" id="toolbar_sectionlist_tooltip" style="display: none; left: 169px; top: -7px;"><span class="inner" style="font-size: 11px; color: #ffffff;"><nobr>Sections</nobr></span><div style="" class="tooltip_tail"></div></div><a class="ctl_button section_list" id="toolbar_sectionlist"></a></div></div><div class="autogen_class_views_documents_fourgen_sections" id="autogen_id_538573386"><div class="popup" id="sectionlist_popup" style="display: none;"><div class="content_wrapper_wrapper"><div class="content_wrapper"><div class="content clearfix"><div id="section_list_container"><div class="header clearfix" style="text-align: left;"><span class="section_title">Sections</span><span class="section_info"></span><span class="controls"><span class="section_counter">Section <span class="notranslate" id="popup_section_number">1</span> of <span class="notranslate">46</span></span><a class="previous" rel="nofollow"> </a><a class="next" rel="nofollow"> </a><a class="close_button" rel="nofollow"></a></span></div><ul class="notranslate" data-section_count="45"><li id="popup_section_link_1"><a class="section_link" data-section="1" href="http://www.scribd.com/doc/61105136/1/M%E1%BA%ADt-ma-h%E1%BB%8Dc-khoa-cong-khai-Phi-%C4%91%E1%BB%91i-x%E1%BB%A9ng-la-gi"><span class="name">1.1.1.1. Mật mã học khóa công khai (Phi đối xứng) là gì</span><span class="page" data-page="9">p. 9</span></a></li><li id="popup_section_link_2"><a class="section_link" data-section="2" href="http://www.scribd.com/doc/61105136/2/M%E1%BB%A5c-%C4%91ich-c%E1%BB%A7a-h%E1%BB%87-th%E1%BB%91ng-ma-hoa-cong-khai"><span class="name">1.1.1.2.Mục đích của hệ thống mã hoá công khai :</span><span class="page" data-page="9">p. 9</span></a></li><li id="popup_section_link_3"><a class="section_link" data-section="3" href="http://www.scribd.com/doc/61105136/3/%E1%BB%A8ng-d%E1%BB%A5ng"><span class="name">1.1.2.Ứng dụng</span><span class="page" data-page="11">p. 11</span></a></li><li id="popup_section_link_4"><a class="section_link" data-section="4" href="http://www.scribd.com/doc/61105136/4/Thu%E1%BA%ADt-toan"><span class="name">1.2.1.Thuật toán</span><span class="page" data-page="12">p. 12</span></a></li><li id="popup_section_link_5"><a class="section_link" data-section="5" href="http://www.scribd.com/doc/61105136/5/Tinh-hi%E1%BB%87u-qu%E1%BA%A3-c%E1%BB%A7a-thu%E1%BA%ADt-toan"><span class="name">1.2.2.1.Tính hiệu quả của thuật toán</span><span class="page" data-page="12">p. 12</span></a></li><li id="popup_section_link_6"><a class="section_link" data-section="6" href="http://www.scribd.com/doc/61105136/6/%C4%90anh-gia-th%E1%BB%9Di-gian-th%E1%BB%B1c-hi%E1%BB%87n-thu%E1%BA%ADt-toan"><span class="name">1.2.2.2.Đánh giá thời gian thực hiện thuật toán</span><span class="page" data-page="12">p. 12</span></a></li><li id="popup_section_link_7"><a class="section_link" data-section="7" href="http://www.scribd.com/doc/61105136/7/PKI-la-gi"><span class="name">1.3.1.PKI là gì</span><span class="page" data-page="13">p. 13</span></a></li><li id="popup_section_link_8"><a class="section_link" data-section="8" href="http://www.scribd.com/doc/61105136/8/C%E1%BB%9F-s%E1%BB%9F-h%E1%BA%A1-t%E1%BA%A7ng-khoa-cong-khai"><span class="name">1.3.2.Cở sở hạ tầng khóa công khai</span><span class="page" data-page="13">p. 13</span></a></li><li id="popup_section_link_9"><a class="section_link" data-section="9" href="http://www.scribd.com/doc/61105136/9/M%E1%BB%99t-s%E1%BB%91-%E1%BB%A9ng-d%E1%BB%A5ng"><span class="name">1.4.1.Một số ứng dụng</span><span class="page" data-page="15">p. 15</span></a></li><li id="popup_section_link_10"><a class="section_link" data-section="10" href="http://www.scribd.com/doc/61105136/10/M%E1%BB%99t-s%E1%BB%91-h%E1%BB%87-th%E1%BB%91ng-PKI"><span class="name">1.4.2.Một số hệ thống PKI</span><span class="page" data-page="15">p. 15</span></a></li><li id="popup_section_link_11"><a class="section_link" data-section="11" href="http://www.scribd.com/doc/61105136/11/M%E1%BB%A5c-%C4%91ich-c%E1%BB%A7a-%C4%91%E1%BB%81-tai"><span class="name">1.5.Mục đích của đề tài</span><span class="page" data-page="16">p. 16</span></a></li><li id="popup_section_link_12"><a class="section_link" data-section="12" href="http://www.scribd.com/doc/61105136/12/%C4%90%E1%BA%B7t-v%E1%BA%A7n-%C4%91%E1%BB%81"><span class="name">1.6.Đặt vần đề ?</span><span class="page" data-page="16">p. 16</span></a></li><li id="popup_section_link_13"><a class="section_link" data-section="13" href="http://www.scribd.com/doc/61105136/13/Cac-v%E1%BA%A5n-%C4%91%E1%BB%81-s%E1%BA%BD-gi%E1%BA%A3i-quy%E1%BA%BFt-trong-khoa-lu%E1%BA%ADn"><span class="name">1.7.Các vấn đề sẽ giải quyết trong khóa luận</span><span class="page" data-page="17">p. 17</span></a></li><li id="popup_section_link_14"><a class="section_link" data-section="14" href="http://www.scribd.com/doc/61105136/14/Ham-b%C4%83m"><span class="name">2.1.1.Hàm băm</span><span class="page" data-page="18">p. 18</span></a></li><li id="popup_section_link_15"><a class="section_link" data-section="15" href="http://www.scribd.com/doc/61105136/15/Ham-b%C4%83m-m%E1%BA%ADt-ma-h%E1%BB%8Dc"><span class="name">2.1.2.Hàm băm mật mã học</span><span class="page" data-page="18">p. 18</span></a></li><li id="popup_section_link_16"><a class="section_link" data-section="16" href="http://www.scribd.com/doc/61105136/16/%C4%90%E1%BA%A3m-b%E1%BA%A3o-tinh-toan-v%E1%BA%B9n-d%E1%BB%AF-li%E1%BB%87u"><span class="name">2.1.3.Đảm bảo tính toàn vẹn dữ liệu</span><span class="page" data-page="18">p. 18</span></a></li><li id="popup_section_link_17"><a class="section_link" data-section="17" href="http://www.scribd.com/doc/61105136/17/Thu%E1%BA%ADt-toan-ham-b%C4%83m-MD5"><span class="name">2.1.4.1.Thuật toán hàm băm MD5</span><span class="page" data-page="19">p. 19</span></a></li><li id="popup_section_link_18"><a class="section_link" data-section="18" href="http://www.scribd.com/doc/61105136/18/Chu%E1%BA%A9n-b%C4%83m-an-toan-SHS"><span class="name">2.1.4.2. Chuẩn băm an toàn SHS</span><span class="page" data-page="20">p. 20</span></a></li><li id="popup_section_link_19"><a class="section_link" data-section="19" href="http://www.scribd.com/doc/61105136/19/Ma-hoa-thong-tin"><span class="name">2.2.Mã hóa thông tin</span><span class="page" data-page="21">p. 21</span></a></li><li id="popup_section_link_20"><a class="section_link" data-section="20" href="http://www.scribd.com/doc/61105136/20/Ch%E1%BB%AF-k%C3%BD-s%E1%BB%91"><span class="name">2.3.1.Chữ ký số</span><span class="page" data-page="22">p. 22</span></a></li><li id="popup_section_link_21"><a class="section_link" data-section="21" href="http://www.scribd.com/doc/61105136/21/Cac-thu%E1%BA%ADt-toan-ch%E1%BB%AF-k%C3%BD-s%E1%BB%91-thong-d%E1%BB%A5ng"><span class="name">2.3.2.1.Các thuật toán chữ ký số thông dụng</span><span class="page" data-page="23">p. 23</span></a></li><li id="popup_section_link_22"><a class="section_link" data-section="22" href="http://www.scribd.com/doc/61105136/22/Thu%E1%BA%ADt-toan-ch%E1%BB%AF-k%C3%BD-s%E1%BB%91-RSA"><span class="name">2.3.2.2.Thuật toán chữ ký số RSA</span><span class="page" data-page="23">p. 23</span></a></li><li id="popup_section_link_23"><a class="section_link" data-section="23" href="http://www.scribd.com/doc/61105136/23/Thu%E1%BA%ADt-toan-ch%E1%BB%AF-k%C3%BD-s%E1%BB%91-DSA"><span class="name">2.3.2.3. Thuật toán chữ ký số DSA</span><span class="page" data-page="24">p. 24</span></a></li><li id="popup_section_link_24"><a class="section_link" data-section="24" href="http://www.scribd.com/doc/61105136/24/K%E1%BA%BFt-qu%E1%BA%A3-th%E1%BB%AD-nghi%E1%BB%87m-va-nh%E1%BA%ADn-xet"><span class="name">2.3.2.4. Kết quả thử nghiệm và nhận xét</span><span class="page" data-page="26">p. 26</span></a></li><li id="popup_section_link_25"><a class="section_link" data-section="25" href="http://www.scribd.com/doc/61105136/25/Ch%E1%BB%A9ng-th%E1%BB%B1c-s%E1%BB%91"><span class="name">2.4.Chứng thực số</span><span class="page" data-page="30">p. 30</span></a></li><li id="popup_section_link_26"><a class="section_link" data-section="26" href="http://www.scribd.com/doc/61105136/26/C%E1%BA%A5u-truc-phan-t%E1%BA%A7ng-c%E1%BB%A7a-h%E1%BB%87-th%E1%BB%91ng-PKI"><span class="name">2.5.Cấu trúc phân tầng của hệ thống PKI</span><span class="page" data-page="30">p. 30</span></a></li><li id="popup_section_link_27"><a class="section_link" data-section="27" href="http://www.scribd.com/doc/61105136/27/C%E1%BA%A5p-phat-ch%E1%BB%A9ng-th%E1%BB%B1c-s%E1%BB%91"><span class="name">2.6.1.Cấp phát chứng thực số</span><span class="page" data-page="31">p. 31</span></a></li><li id="popup_section_link_28"><a class="section_link" data-section="28" href="http://www.scribd.com/doc/61105136/28/Xac-th%E1%BB%B1c-ch%E1%BB%A9ng-th%E1%BB%B1c-s%E1%BB%91"><span class="name">2.6.2.Xác thực chứng thực số</span><span class="page" data-page="32">p. 32</span></a></li><li id="popup_section_link_29"><a class="section_link" data-section="29" href="http://www.scribd.com/doc/61105136/29/Ma-hoa"><span class="name">2.7.1.Mã hóa</span><span class="page" data-page="33">p. 33</span></a></li><li id="popup_section_link_30"><a class="section_link" data-section="30" href="http://www.scribd.com/doc/61105136/30/Ch%E1%BB%91ng-gi%E1%BA%A3-m%E1%BA%A1o"><span class="name">2.7.2.Chống giả mạo</span><span class="page" data-page="33">p. 33</span></a></li><li id="popup_section_link_31"><a class="section_link" data-section="31" href="http://www.scribd.com/doc/61105136/31/Xac-th%E1%BB%B1c"><span class="name">2.7.3.Xác thực</span><span class="page" data-page="34">p. 34</span></a></li><li id="popup_section_link_32"><a class="section_link" data-section="32" href="http://www.scribd.com/doc/61105136/32/Ch%E1%BB%91ng-ch%E1%BB%91i-b%E1%BB%8F-ngu%E1%BB%93n-g%E1%BB%91c"><span class="name">2.7.4.Chống chối bỏ nguồn gốc</span><span class="page" data-page="34">p. 34</span></a></li><li id="popup_section_link_33"><a class="section_link" data-section="33" href="http://www.scribd.com/doc/61105136/33/Ch%E1%BB%AF-k%C3%BD-%C4%91i%E1%BB%87n-t%E1%BB%AD"><span class="name">2.7.5.Chữ ký điện tử</span><span class="page" data-page="34">p. 34</span></a></li><li id="popup_section_link_34"><a class="section_link" data-section="34" href="http://www.scribd.com/doc/61105136/34/B%E1%BA%A3o-m%E1%BA%ADt-website"><span class="name">2.7.6.Bảo mật website</span><span class="page" data-page="35">p. 35</span></a></li><li id="popup_section_link_35"><a class="section_link" data-section="35" href="http://www.scribd.com/doc/61105136/35/%C4%90%E1%BA%A3m-b%E1%BA%A3o-ph%E1%BA%A7n-m%E1%BB%81m"><span class="name">2.7.7.Đảm bảo phần mềm</span><span class="page" data-page="35">p. 35</span></a></li><li id="popup_section_link_36"><a class="section_link" data-section="36" href="http://www.scribd.com/doc/61105136/36/%C4%90%E1%BB%8Bnh-ngh%C4%A9a"><span class="name">2.8.1.Định nghĩa :</span><span class="page" data-page="35">p. 35</span></a></li><li id="popup_section_link_37"><a class="section_link" data-section="37" href="http://www.scribd.com/doc/61105136/37/%C6%AFu-%C4%91i%E1%BB%83m-c%E1%BB%A7a-h%E1%BB%87-th%E1%BB%91ng"><span class="name">2.8.2.1.Ưu điểm của hệ thống</span><span class="page" data-page="36">p. 36</span></a></li><li id="popup_section_link_38"><a class="section_link" data-section="38" href="http://www.scribd.com/doc/61105136/38/Nh%E1%BB%AFng-%C4%91i%E1%BB%83m-con-h%E1%BA%A1n-ch%E1%BA%BF-c%E1%BB%A7a-h%E1%BB%87-th%E1%BB%91ng"><span class="name">2.8.2.2.Những điểm còn hạn chế của hệ thống</span><span class="page" data-page="36">p. 36</span></a></li><li id="popup_section_link_39"><a class="section_link" data-section="39" href="http://www.scribd.com/doc/61105136/39/Ngon-ng%E1%BB%AF-l%E1%BA%ADp-trinh"><span class="name">3.1.Ngôn ngữ lập trình</span><span class="page" data-page="37">p. 37</span></a></li><li id="popup_section_link_40"><a class="section_link" data-section="40" href="http://www.scribd.com/doc/61105136/40/Th%C6%B0-vi%E1%BB%87n-s%E1%BB%91-nguyen-l%E1%BB%9Bn"><span class="name">3.2.Thư viện số nguyên lớn</span><span class="page" data-page="37">p. 37</span></a></li><li id="popup_section_link_41"><a class="section_link" data-section="41" href="http://www.scribd.com/doc/61105136/41/C%E1%BA%A5p-phat"><span class="name">3.3.1.Cấp phát</span><span class="page" data-page="37">p. 37</span></a></li><li id="popup_section_link_42"><a class="section_link" data-section="42" href="http://www.scribd.com/doc/61105136/42/Ch%E1%BB%A9ng-th%E1%BB%B1c"><span class="name">3.3.2.Chứng thực</span><span class="page" data-page="49">p. 49</span></a></li><li id="popup_section_link_43"><a class="section_link" 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<span class="a" style="left:836px;top:841px;word-spacing:1px">Tôi xin gửi lời cảm ơn chân thành nhất tới PGS.TS Hồ Sĩ Đàm, TS. Lê Đức Phong.</span><span class="a" style="left:603px;top:984px;word-spacing:3px">&nbsp;Những người thầy đã cho tôi những định hướng và những ý kiến rất quý báu để tôi hoàn</span><span class="a" style="left:627px;top:1127px;word-spacing:3px">thành được khóa luận tốt nghiệp này. Tôi xin tỏ lòng biết ơn sâu sắc tới các thầy cô, bạn</span><span class="a" style="left:603px;top:1270px;word-spacing:3px">&nbsp;bè đã dìu dắt, giúp đỡ tôi tiến bộ trong suốt quá trình làm khóa luận tốt nghiệp. Xin cảm</span><span class="a" style="left:627px;top:1413px;word-spacing:5px;letter-spacing:1px">ơn gia đình và bè bạn, những người luôn khuyến khích và giúp đỡ tôi trong mọi hoàn</span><span class="a" style="left:627px;top:1556px;word-spacing:4px;letter-spacing:1px">cảnh khó khăn. Tôi xin cảm ơn bộ môn Truyền Thông và Mạng Máy Tính, khoa Công</span><span class="a" style="left:603px;top:1699px;word-spacing:2px;letter-spacing:1px">&nbsp;Nghệ Thông Tin trường Đại Học Công Nghệ-Đại Học Quốc Gia Hà Nội đã hết sức tạo</span><span class="a" style="left:627px;top:1842px;word-spacing:-2px">điều kiện cho tôi trong quá <span class="w6"></span>trình học, làm và hoàn <span class="w6"></span>thành khóa luận này.</span></div>
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Thuận...........................................................................................................................1</span><span class="a" style="left:738px;top:1078px;word-spacing:-3px;color:#0000ff"><a href="javascript:%20window.location.hash='#outer_page_1'" class="ll" orig="cGFnZTE=">HÀ NỘI - <span class="w7"></span>2010 <span class="l" style="margin-left:-19px">.................................................<span class="w6"></span>..................................................<span class="w6"></span>........<span class="w6"></span>.......<span class="w6"></span>.......<span class="w6"></span>.. <span class="l" style="margin-left:-17px">1</span></span></a></span><span class="a" style="left:627px;top:1180px;word-spacing:14px">Trần
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Thuận...........................................................................................................................2</span><span class="a" style="left:627px;top:1281px;word-spacing:4px;letter-spacing:1px">Khóa luận “Hạ tầng khóa công khai (PKI), vấn đề cấp phát chứng thực số và ứng dụng trong</span><span class="a" style="left:627px;top:1383px;word-spacing:1px;letter-spacing:1px">thương mại điện tử”. Hạ tầng khóa công khai là một bộ khung cơ bản để xây dựng mô hình an</span><span class="a" style="left:627px;top:1485px;letter-spacing:1px">ninh, bảo mật trong thương mại điện tử. Tìm hiểu vai trò của chứng thực số trong hạ tầng khóa</span><span class="a" style="left:627px;top:1586px;word-spacing:3px">công khai. Vai trò của chứng thực số trong các giao dịch trực tuyến. Người sử dụng, ngoài hình</span><span class="a" style="left:627px;top:1688px;word-spacing:-1px;letter-spacing:1px">thức bảo mật thông thường như mật khẩu, cũng phải dùng <span class="w6"></span>một chứng thực số cá nhân <span class="w6"></span>để khẳng</span><span class="a" style="left:627px;top:1790px;word-spacing:5px;letter-spacing:1px">định danh tính của mình, xác nhận các hoạt động giao dịch của mình với dịch vụ ngân hàng,</span><span class="a" style="left:627px;top:1891px;word-spacing:2px;letter-spacing:1px">thương mại điện tử, dao dịch chứng khoán... Chứng thực số sẽ giúp nhà quản lý đảm bảo rằng</span><span class="a" style="left:627px;top:1993px;word-spacing:3px">khách hàng không thể chối cãi các giao dịch của mình, khi họ đã dùng chứng thực số. Từ đó đặt</span><span class="a" style="left:627px;top:2095px;word-spacing:1px">ra các vấn đề quản lý (cấp phát,xác thực) thu hồi và cấp phát lại chứng thực số............................5</span><span class="a" style="left:627px;top:2197px;word-spacing:-2px;letter-spacing:1px">Trong khóa luận tôi sẽ trình bày về các <span class="w6"></span>vấn đề chính xoay quanh vấn <span class="w6"></span>đề hạ tầng khóa <span class="w7"></span>công khai</span><span class="a" style="left:627px;top:2298px">(PKI). Phần đầu của khóa luận (chương 1) giới thiệu vấn đề và cách tiếp cận giải quyết vấn đề sẽ</span><span class="a" style="left:627px;top:2400px;word-spacing:3px;letter-spacing:1px">trình bày khái quát về một vài khái niệm cơ bản về mật mã học khóa công khai, hạ tầng khóa</span><span class="a" style="left:627px;top:2502px;word-spacing:3px;letter-spacing:1px">công khai ; các khái niệm cơ bản về thuật toán và lý thuyết độ phức tạp; một vài công cụ nền</span><span class="a" style="left:627px;top:2603px;word-spacing:4px;letter-spacing:1px">tảng của mật mã học khóa công khai (mã hóa thông tin, hàm băm, chữ ký số). Chương 2 của</span><span class="a" style="left:627px;top:2705px;word-spacing:2px;letter-spacing:2px">khóa luận sẽ làm rõ hơn các khái niệm, các vấn đề cơ bản bên trong một hạ tầng khóa công</span><span class="a" style="left:627px;top:2807px;word-spacing:1px;letter-spacing:1px">khai (chứng thực số, các dịch vụ đăng ký, cấp phát, xác thực, thu hồi, … khóa công khai); ứng</span><span class="a" style="left:627px;top:2908px;word-spacing:3px">dụng của hạ tầng khóa công khai trong giao dịch điện tử ngày nay ; và một vài hệ thống hạ tầng</span><span class="a" style="left:627px;top:3010px;word-spacing:2px;letter-spacing:2px">khóa công khai trong thực tế. Chương 3 đặc tả một hạ tầng khóa công khai đơn giản và Kết</span><span class="a" style="left:627px;top:3112px">Luận.................................................................................................................................................5</span></div>
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<span class="a" style="left:836px;top:951px;word-spacing:5px">Khóa luận</span></div>
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<span class="a" style="left:1269px;top:952px;word-spacing:1px;letter-spacing:1px">“Hạ tầng khóa công khai (PKI), vấn đề cấp phát chứng thực số và ứng&nbsp;</span><span class="a" style="left:627px;top:1095px;word-spacing:2px">dụng trong thương mại điện tử”</span></div>
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<span class="a" style="left:1877px;top:1094px;word-spacing:3px">. Hạ tầng khóa công khai là một bộ khung cơ bản để xây</span><span class="a" style="left:627px;top:1237px;word-spacing:-1px">dựng mô hình an ninh, bảo mật trong thương mại điện <span class="w6"></span>tử. Tìm hiểu vai trò của chứng thực</span><span class="a" style="left:627px;top:1380px;word-spacing:-1px">số trong hạ tầng <span class="w6"></span>khóa công khai. V<span class="l8">ai trò của chứng thực <span class="w6"></span>số trong các giao dịch trực <span class="w7"></span>tuyến.</span></span><span class="a" style="left:603px;top:1523px;word-spacing:-1px">&nbsp;Người sử dụng, ngoài hình <span class="w6"></span>thức bảo mật thông thường như mật khẩu, <span class="w6"></span>cũng phải dùng một</span><span class="a" style="left:627px;top:1666px;word-spacing:2px;letter-spacing:1px">chứng thực số cá nhân để khẳng định danh tính của mình, xác nhận các hoạt động giao</span><span class="a" style="left:627px;top:1809px;word-spacing:-1px">dịch của mình với dịch vụ ngân <span class="w6"></span>hàng, thương mại điện tử, dao dịch chứng <span class="w6"></span>khoán... Chứng</span><span class="a" style="left:627px;top:1952px;word-spacing:2px;letter-spacing:1px">thực số sẽ giúp nhà quản lý đảm bảo rằng khách hàng không thể chối cãi các giao dịch</span><span class="a" style="left:627px;top:2095px;word-spacing:1px;letter-spacing:1px">của mình, khi họ đã dùng chứng thực số. Từ đó đặt ra các vấn đề quản lý (cấp phát,xác</span><span class="a" style="left:627px;top:2238px;word-spacing:-1px">thực) thu hồi và cấp phát lại chứng thực số.</span><span class="a" style="left:836px;top:2425px;word-spacing:1px;letter-spacing:2px">Trong khóa luận tôi sẽ trình bày về các vấn đề chính xoay quanh vấn đề hạ tầng</span><span class="a" style="left:627px;top:2568px;word-spacing:3px">khóa công khai (PKI). Phần đầu của khóa luận (chương 1) giới thiệu vấn đề và cách tiếp</span><span class="a" style="left:627px;top:2711px;word-spacing:4px">cận giải quyết vấn đề sẽ trình bày khái quát về một vài khái niệm cơ bản về mật mã học</span><span class="a" style="left:627px;top:2854px;word-spacing:2px">khóa công khai, hạ tầng khóa công khai ; các khái niệm cơ bản về thuật toán và lý thuyết</span><span class="a" style="left:627px;top:2997px">độ phức tạp; một vài công cụ nền tảng của mật mã học khóa công khai (mã hóa thông tin,</span><span class="a" style="left:627px;top:3140px;word-spacing:-1px">hàm băm, chữ ký số). Chương 2 của khóa luận sẽ làm rõ hơn các khái niệm, các vấn đề cơ&nbsp;</span><span class="a" style="left:603px;top:3283px;word-spacing:1px">&nbsp;bản bên trong một hạ tầng khóa công khai (chứng thực số, các dịch vụ đăng ký, cấp phát,</span><span class="a" style="left:627px;top:3426px;word-spacing:2px;letter-spacing:1px">xác thực, thu hồi, … khóa công khai); ứng dụng của hạ tầng khóa công khai trong giao</span><span class="a" style="left:627px;top:3569px;word-spacing:-1px">dịch điện tử ngày nay ; <span class="w6"></span>và một vài hệ thống hạ <span class="w6"></span>tầng khóa công khai trong thực tế. Chương</span><span class="a" style="left:627px;top:3712px;word-spacing:-1px">3 đặc tả một hạ tầng khóa công khai đơn giản và Kết Luận.</span></div>
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<span class="a" style="left:1477px;top:661px">DANH MỤC HÌNH VẼ VÀ BẢNG</span></div>
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<span class="a" style="left:893px;top:977px;word-spacing:-1px">Hình 1.1: Cấp phát khóa riêng khóa công khai</span><span class="a" style="left:893px;top:1164px;word-spacing:-1px">Hình 1.2: Mã hóa thông tin</span><span class="a" style="left:893px;top:1351px;word-spacing:2px">Hình 1.3: <span class="w" style="width:18px"></span>Tạo và x<span class="l6">ác thực <span class="l6">chữ ký số</span></span></span><span class="a" style="left:893px;top:1538px;word-spacing:-1px">Hình 1.4 : Mô hình xây dựng PKI cơ bản</span><span class="a" style="left:893px;top:1726px;word-spacing:-1px">Bảng 1.5 : mô hình xử dụng xác thực</span><span class="a" style="left:893px;top:1913px;word-spacing:-2px">Hình 2.1 : Đặc <span class="w6"></span>điểm của các thuật toán băm SHA</span><span class="a" style="left:893px;top:2100px;word-spacing:2px">Bảng 2.2 :So sánh thời gian tạo khóa, tạo chữ ký và xác nhận chữ ký của RSA với</span><span class="a" style="left:893px;top:2243px">DSA</span><span class="a" style="left:893px;top:2430px;word-spacing:-1px">Hình 2.3 : Thời gian xác nhận chữ ký của RSA và DSA</span><span class="a" style="left:893px;top:2617px;word-spacing:-1px">Hình 2.4 : Thời gian tạo chữ ký của RSA và DSA</span><span class="a" style="left:893px;top:2804px;word-spacing:-1px">Hình 2.5 : Thời gian xác nhận chữ ký của RSA và DSA</span><span class="a" style="left:893px;top:2992px;word-spacing:-1px">Hình 2.6 : Mô hình phân cấp</span><span class="a" style="left:893px;top:3179px;word-spacing:-1px">Hình 3.1 : Hàm tạo cặp khóa riêng và khóa công khai</span><span class="a" style="left:893px;top:3366px;word-spacing:-1px">Hình 3.2 : Mô phỏng tạo khóa</span><span class="a" style="left:893px;top:3553px;word-spacing:-1px">Hình 3.3 : Tạo chữ ký số</span><span class="a" style="left:893px;top:3740px;word-spacing:-2px">Hình 3.4 : Form nhập <span class="w6"></span>thông tin của client</span><span class="a" style="left:893px;top:3928px;word-spacing:-1px">Hình 3.5 : Thông báo trả về khi kết quả gửi thông tin thành công</span><span class="a" style="left:893px;top:4115px;word-spacing:-1px">Hình 3.6 : Xác thực khóa công khai và chữ ký số</span><span class="a" style="left:893px;top:4302px;word-spacing:2px">Hình 3.7 : <span class="w" style="width:16px"></span>cấp phát <span class="l6">chứng thực <span class="l6">số</span></span></span><span class="a" style="left:893px;top:4489px;word-spacing:-1px">Hình 3.8 : Kiểm tra thông tin và cấp phát chứng thực số</span><span class="a" style="left:893px;top:4676px;word-spacing:-1px">Hình 3.9 : Xác thực chứng thực số</span><span class="a" style="left:893px;top:4863px;word-spacing:-1px">Hình 3.10 : Form tìm kiếm, sửa, xóa thông tin chứng thực số</span><span class="a" style="left:893px;top:5051px;word-spacing:-1px">Hình 3.11 : Kiểm tra và thu hồi chứng thực số hết hạn sử dụng</span></div>
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<span class="a" style="left:2126px;top:578px;word-spacing:-1px">Mở Đầu</span></div>
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<span class="a" style="left:836px;top:1082px;word-spacing:1px;letter-spacing:1px">Trong kỷ nguyên của công nghệ thông tin, tính phổ biến rộng rãi của Internet một</span><span class="a" style="left:627px;top:1225px;word-spacing:2px;letter-spacing:1px">mặt đem lại nhiều ứng dụng tiện lợi, thú vị và dần thay thế các hoạt động truyền thống</span><span class="a" style="left:627px;top:1367px;word-spacing:2px;letter-spacing:1px">trong thế giớ thực; mặt khác nó đặt ra các vấn đề về sự an toàn, tính tin cậy của những</span><span class="a" style="left:627px;top:1510px;word-spacing:3px;letter-spacing:1px">giao dịch trên Internet. Cơ sở hạ tầng khóa công khai (PKI) có thể đáp ứng, giải quyết</span><span class="a" style="left:627px;top:1653px;word-spacing:1px">những vấn đề cơ bản nhất cho những yêu cầu trên. Dựa trên các dịch vụ cơ bản về chứng</span><span class="a" style="left:627px;top:1796px;word-spacing:4px;letter-spacing:1px">thực số và chữ ký số, một PKI chính là bộ khung của các chính sách, dịch vụ và phần</span><span class="a" style="left:627px;top:1939px;word-spacing:-1px">mềm mã hóa, đáp ứng nhu cầu bảo mật của người sử dụng.</span><span class="a" style="left:836px;top:2127px;word-spacing:3px">Không chỉ nằm trong lĩnh vực thương mại điện tử, chứng thực số hiện còn được sử</span><span class="a" style="left:627px;top:2269px;word-spacing:1px;letter-spacing:1px">dụng như một dạng chứng minh thư cá nhân. Tại các nước công nghệ phát triển, chứng</span><span class="a" style="left:627px;top:2412px;word-spacing:2px">thực số CA được tích hợp vào các chip nhớ nằm trong thẻ căn cước, thẻ tín dụng để tăng</span><span class="a" style="left:627px;top:2555px;word-spacing:4px">cường khả năng bảo mật, chống giả mạo, cho phép chủ thẻ xác thực danh tính của mình</span><span class="a" style="left:627px;top:2698px;word-spacing:3px;letter-spacing:1px">trên nhiều hệ thống khác nhau, chẳng hạn như xe bus, thẻ rút tiền ATM, kiểm soát hải</span><span class="a" style="left:627px;top:2841px;word-spacing:-1px">quan, ra vào chung cư .v.v.</span><span class="a" style="left:836px;top:3029px;word-spacing:-1px">Với các đặc điểm nổi bật như không thể giả mạo, chứng thực nguồn gốc xuất xứ, các</span><span class="a" style="left:627px;top:3171px;word-spacing:-1px">quốc gia phát triển đều đã sử <span class="w7"></span>dụng chứng thực số như <span class="w6"></span>một bằng chứng pháp lý từ rất <span class="w6"></span>sớm.</span><span class="a" style="left:627px;top:3314px;word-spacing:-1px">Đây là yếu tố rất quan <span class="w6"></span>trọng để có thể phát triển thương <span class="w6"></span>mại điện tử, vì không ai dám <span class="w6"></span>mạo</span><span class="a" style="left:627px;top:3457px;word-spacing:2px">hiểm với tiền của mình, khi họ chưa chắc chắn được rằng các hoạt động đó có được đảm</span><span class="a" style="left:603px;top:3600px;word-spacing:-1px">&nbsp;bảo, và có được pháp luật công nhận hay không</span></div>
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<span class="a" style="left:2459px;top:3613px">.</span></div>
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<span class="a" style="left:836px;top:3788px;word-spacing:1px">Trong bản khóa luận tốt nghiệp này, tác giả xin trình bày tổng quát về cơ sở hạ tầng</span><span class="a" style="left:627px;top:3931px;word-spacing:4px">khóa công khai và ứng dụng của nó trong thương mại điện tử. Qua đó trình bày một bản</span><span class="a" style="left:603px;top:4073px;word-spacing:-2px">&nbsp;platform mô phỏng hoạt động của <span class="w6"></span>một hạ tầng khóa công khai <span class="w6"></span>(PKI) cơ bản.</span><span class="a" style="left:627px;top:5247px">&nbsp;</span></div>
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<span class="a" style="left:2263px;top:5253px">1</span></div>
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<span class="a" style="left:1716px;top:578px;word-spacing:-1px">Chương 1 : Giới Thiệu</span></div>
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<span class="a" style="left:627px;top:1076px;letter-spacing:-1px">1.1.</span></div>
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<span class="a" style="left:893px;top:1059px">Tìm hiểu Mật mã học khoá công khai</span></div>
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<span class="a" style="left:694px;top:1295px">1.1.1.</span></div>
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<span class="a" style="left:1158px;top:1291px;word-spacing:2px;letter-spacing:-1px">Mật mã học khoá công khai</span></div>
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<span class="a" style="left:2382px;top:1292px">&nbsp;</span></div>
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<span class="a" style="left:760px;top:1504px">1.1.1.1.</span></div>
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<span class="a" style="left:1423px;top:1500px;word-spacing:-2px">Mật mã học khóa công khai (Phi đối xứng) là <span class="w7"></span>gì</span></div>
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<span class="a" style="left:1092px;top:1725px">-</span></div>
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<span class="a" style="left:1158px;top:1701px;word-spacing:4px">là một chuyên ngành của mật mã học cho phép người sử dụng trao đổi các</span><span class="a" style="left:1092px;top:1844px;word-spacing:4px;letter-spacing:1px">thông tin mật mà không cần phải trao đổi các khóa chung bí mật trước đó.</span><span class="a" style="left:1092px;top:1987px;word-spacing:4px;letter-spacing:1px">Điều này được thực hiện bằng cách sử dụng một cặp khóa có quan hệ toán</span><span class="a" style="left:1092px;top:2129px;word-spacing:-2px">học với nhau là</span></div>
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<span class="a" style="left:1706px;top:2128px;word-spacing:4px;letter-spacing:-1px">khóa công khai</span></div>
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<span class="a" style="left:2353px;top:2129px">và</span></div>
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<span class="a" style="left:2467px;top:2128px;word-spacing:3px;letter-spacing:-1px">khóa cá nhân</span></div>
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<span class="a" style="left:3040px;top:2129px;word-spacing:-2px">(hay khóa bí mật).</span></div>
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<span class="a" style="left:959px;top:2341px">-</span></div>
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<span class="a" style="left:1092px;top:2317px;word-spacing:4px">Trong mật mã học khóa công khai, khóa cá nhân phải được giữ bí mật trong</span><span class="a" style="left:1092px;top:2460px;word-spacing:3px">khi khóa công khai được phổ biến công khai. Trong 2 khóa, một dùng để mã</span><span class="a" style="left:1092px;top:2603px;word-spacing:2px;letter-spacing:2px">hóa và khóa còn lại dùng để giải mã. Điều quan trọng đối với hệ thống là</span><span class="a" style="left:1092px;top:2746px;word-spacing:-2px">không thể tìm ra khóa bí <span class="w7"></span>mật nếu chỉ biết khóa công khai.[1]</span></div>
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<span class="a" style="left:627px;top:2940px;word-spacing:-5px;letter-spacing:3px">1.<span class="l6">1.<span class="l6">1.<span class="l6">2.<span class="w" style="width:104px"></span>Mụ<span class="l8">c đí<span class="l8">ch c<span class="l8">ủa <span class="l6">hệ t<span class="l8">hố<span class="l7">ng m<span class="l9">ã ho<span class="l8">á cô<span class="l7">ng k<span class="l9">ha<span class="l7">i :</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></div>
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<span class="a" style="left:959px;top:3162px">-</span></div>
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<span class="a" style="left:1092px;top:3136px;word-spacing:-2px">Cấp phát khoá riêng và khoá công khai :</span><span class="a" style="left:1775px;top:4367px;word-spacing:-2px">Hình 1.1: Cấp phát khóa riêng khóa công khai</span></div>
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<span class="a" style="left:1356px;top:4788px"></span></div>
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<span class="a" style="left:1490px;top:4760px;word-spacing:4px">Việc cấp phát khoá công khai và khoá bí mật thông qua thuật toán</span><span class="a" style="left:1488px;top:4903px;word-spacing:2px">RSA (phổ biến). Thuật toán RSA tạo ra cặp khoá bằng các phương</span><span class="a" style="left:1488px;top:5046px;word-spacing:-1px">thức toán học từ 2 số nguyên tố bất kỳ đủ lớn.</span><span class="a" style="left:627px;top:5247px">&nbsp;</span></div>
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<span class="a" style="left:2263px;top:5253px">2</span></div>
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&nbsp;
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<span class="a" style="left:893px;top:1295px">&nbsp;</span><span class="a" style="left:959px;top:1485px">-</span></div>
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<span class="a" style="left:1092px;top:1484px;word-spacing:2px;letter-spacing:-1px">Mã hoá :</span><span class="a" style="left:2168px;top:3112px;word-spacing:-2px">Hình 1.2: Mã hóa thông tin</span></div>
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<span class="a" style="left:1356px;top:3533px"></span></div>
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<span class="a" style="left:1490px;top:3505px;word-spacing:10px;letter-spacing:2px">Bob mã hóa thông tin gửi cho Alice bằng khóa công khai của</span><span class="a" style="left:1488px;top:3648px;word-spacing:4px;letter-spacing:1px">Alice. Alice nhận được tin nhắn từ Bob kiểm tra tin nhắn và giải</span><span class="a" style="left:1488px;top:3791px;word-spacing:-2px">mã bằng khóa bí mật của <span class="w6"></span>Alice.</span></div>
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<span class="a" style="left:959px;top:4000px">-</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:1092px;top:3986px;word-spacing:-1px">Tạo và xác thực chữ ký số :</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:627px;top:5247px">&nbsp;</span></div>
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&nbsp;
<div class="ff16" style="font-size:109px">
<span class="a" style="left:2011px;top:1868px;word-spacing:1px">Hình 1.3: <span class="w" style="width:20px"></span>Tạo và xác th<span class="l6">ực chữ k<span class="l6">ý số</span></span></span><span class="a" style="left:2056px;top:2064px;word-spacing:-2px">S = H(m)^d mod n (Tạo <span class="w6"></span>chữ kí số)</span></div>
<div class="ff14" style="font-size:70px">
<span class="a" style="left:1356px;top:2287px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1490px;top:2270px;letter-spacing:1px">Cho phép kiểm tra một văn bản có phải đã được tạo với một khóa</span><span class="a" style="left:1464px;top:2413px;word-spacing:-1px">&nbsp;bí mật nào đó hay không.</span></div>
<div class="ff14" style="font-size:70px">
<span class="a" style="left:1356px;top:2627px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1490px;top:2610px;word-spacing:-2px">Tạo chữ kí số bằng <span class="w6"></span>khóa bí mật của Alice.</span></div>
<div class="ff14" style="font-size:70px">
<span class="a" style="left:1356px;top:2826px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1490px;top:2809px;word-spacing:-1px">Và ký vào tin nhắn Alive gửi cho Bob</span></div>
<div class="ff14" style="font-size:70px">
<span class="a" style="left:1356px;top:3025px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1490px;top:3009px;word-spacing:-1px">Bob kiểm tra chữ ký số bằng khóa công khai của Alice:</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:1490px;top:3197px;word-spacing:7px">S^e m<span class="l6">od n <span class="l8">=H(m) <span class="w" style="width:22px"></span>với H(m<span class="l6">)</span></span></span></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:2689px;top:3199px;word-spacing:2px">là giá trị sau khi băm tin nhắn Alice</span><span class="a" style="left:1490px;top:3342px;word-spacing:-1px">gửi cho Bob. Chữ ký số <span class="w6"></span>đúng đắn đồng nghĩa với việc các thông tin</span><span class="a" style="left:1490px;top:3485px;word-spacing:-1px">Alice gửi bob là đúng đắn.</span></div>
<div class="ff16" style="font-size:117px">
<span class="a" style="left:694px;top:3679px;word-spacing:2px;letter-spacing:2px">1.1<span class="l7">.2.<span class="w" style="width:26px"></span>Ứng <span class="l11">dụn<span class="l8">g</span></span></span></span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:826px;top:3886px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:959px;top:3888px;word-spacing:-1px">Ứng dụng rõ ràng nhất của <span class="w6"></span>mật mã hóa khóa công khai là trong <span class="w6"></span>lĩnh vực bảo mật,</span><span class="a" style="left:959px;top:4031px;word-spacing:5px;letter-spacing:2px">an toàn thông tin: Một văn bản được</span><span class="a" style="left:2512px;top:4031px;word-spacing:4px;letter-spacing:2px"><a rel="nofollow" href="http://vi.wikipedia.org/wiki/M%C3%A3_h%C3%B3a" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvd2lraS9NJUMzJUEzX2glQzMlQjNh">mã hóa</a></span><span class="a" style="left:2848px;top:4031px;letter-spacing:-1px">bằng</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:3074px;top:4029px;word-spacing:7px;letter-spacing:1px">khóa công khai</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:3770px;top:4031px;word-spacing:9px;letter-spacing:1px">của một</span><span class="g" style="top:4174px"><span class="a" style="left:959px">người sử dụng thì chỉ có thể</span><span class="a" style="left:2067px;word-spacing:-1px"><a rel="nofollow" href="http://vi.wikipedia.org/w/index.php?title=Gi%E1%BA%A3i_m%C3%A3&amp;action=edit&amp;redlink=1" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvdy9pbmRleC5waHA/dGl0bGU9R2klRTElQkElQTNpX20lQzMlQTMmYWN0aW9uPWVkaXQmcmVkbGluaz0x">giải mã</a></span><span class="a" style="left:2378px">với</span><span class="a" style="left:2529px;word-spacing:-1px"><a rel="nofollow" href="http://vi.wikipedia.org/w/index.php?title=Kh%C3%B3a_b%C3%AD_m%E1%BA%ADt&amp;action=edit&amp;redlink=1" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvdy9pbmRleC5waHA/dGl0bGU9S2glQzMlQjNhX2IlQzMlQURfbSVFMSVCQSVBRHQmYWN0aW9uPWVkaXQmcmVkbGluaz0x">khóa bí mật</a></span><span class="a" style="left:3008px;word-spacing:-1px">của người đó.Các thuật toán</span></span>
<span class="a" style="left:959px;top:4317px">tạo</span><span class="a" style="left:1109px;top:4317px;word-spacing:4px;letter-spacing:1px"><a rel="nofollow" href="http://vi.wikipedia.org/wiki/Ch%E1%BB%AF_k%C3%BD_s%E1%BB%91" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvd2lraS9DaCVFMSVCQiVBRl9rJUMzJUJEX3MlRTElQkIlOTE=">chữ ký số</a></span><span class="a" style="left:1529px;top:4317px;word-spacing:3px;letter-spacing:1px">khóa công khai cho phép định danh một tin nhắn hay 1 tài liệu .</span><span class="g" style="top:4460px"><span class="a" style="left:959px;word-spacing:2px;letter-spacing:1px">Một người sử dụng có thể</span><span class="a" style="left:2021px;word-spacing:1px;letter-spacing:1px"><a rel="nofollow" href="http://vi.wikipedia.org/wiki/M%C3%A3_h%C3%B3a" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvd2lraS9NJUMzJUEzX2glQzMlQjNh">mã hóa</a></span><span class="a" style="left:2339px;word-spacing:1px;letter-spacing:1px">văn bản với</span><span class="a" style="left:2836px;word-spacing:1px;letter-spacing:1px"><a rel="nofollow" href="http://vi.wikipedia.org/w/index.php?title=Kh%C3%B3a_b%C3%AD_m%E1%BA%ADt&amp;action=edit&amp;redlink=1" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvdy9pbmRleC5waHA/dGl0bGU9S2glQzMlQjNhX2IlQzMlQURfbSVFMSVCQSVBRHQmYWN0aW9uPWVkaXQmcmVkbGluaz0x">khóa bí mật</a></span><span class="a" style="left:3334px;word-spacing:1px;letter-spacing:1px">của mình. Nếu một</span></span>
<span class="a" style="left:959px;top:4603px;word-spacing:4px">người khác có thể giải mã với</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:2162px;top:4601px;word-spacing:2px">khóa công khai</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:2824px;top:4603px;word-spacing:-1px;letter-spacing:1px">của người gửi thì có <span class="w6"></span>thể tin rằng</span><span class="a" style="left:959px;top:4746px;word-spacing:1px">văn bản thực sự xuất phát từ người gắn với khóa công khai đó (Đây là nguyên lý</span><span class="a" style="left:959px;top:4889px;word-spacing:2px">sinh &amp; xác thực chữ ký số, người gửi sử dụng khóa bí mật của mình để sinh ra 1</span><span class="a" style="left:959px;top:5031px;word-spacing:3px;letter-spacing:1px">chữ ký số cho 1 tin nhắn, tài liệu. Bên nhận có thể xác thực tính đúng đắn của</span></div>
<div class="ff21" style="font-size:99px">
<span class="a" style="left:2263px;top:5253px">4</span></div>
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&nbsp;
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<span class="a" style="left:959px;top:526px;word-spacing:1px;letter-spacing:1px">chữ ký số đó nhờ vào khóa công khai của người gửi).Các đặc điểm trên còn có</span><span class="g" style="top:669px"><span class="a" style="left:959px;word-spacing:2px">ích cho nhiều ứng dụng khác như:</span><span class="a" style="left:2311px;word-spacing:1px"><a rel="nofollow" href="http://vi.wikipedia.org/wiki/Ti%E1%BB%81n_%C4%91i%E1%BB%87n_t%E1%BB%AD" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvd2lraS9UaSVFMSVCQiU4MW5fJUM0JTkxaSVFMSVCQiU4N25fdCVFMSVCQiVBRA==">tiền điện tử</a></span><span class="a" style="left:2752px">,</span><span class="a" style="left:2803px;word-spacing:1px"><a rel="nofollow" href="http://vi.wikipedia.org/w/index.php?title=Th%E1%BB%8Fa_thu%E1%BA%ADn_kh%C3%B3a&amp;action=edit&amp;redlink=1" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvdy9pbmRleC5waHA/dGl0bGU9VGglRTElQkIlOEZhX3RodSVFMSVCQSVBRG5fa2glQzMlQjNhJmFjdGlvbj1lZGl0JnJlZGxpbms9MQ==">thỏa thuận khóa</a></span><span class="a" style="left:3420px">...</span></span>
</div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:3493px;top:667px">&nbsp;</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:3543px;top:669px;word-spacing:2px">Các vấn đề và</span><span class="a" style="left:959px;top:812px;word-spacing:-2px">mục đích của đề tài.</span></div>
<div class="ff16" style="font-size:133px">
<span class="a" style="left:627px;top:1007px;word-spacing:-3px;letter-spacing:1px">1.2.<span class="w" style="width:19px"></span>Thuật toá<span class="l6">n và độ phức tạp thu<span class="l6">ật toán</span></span></span></div>
<div class="ff16" style="font-size:117px">
<span class="a" style="left:694px;top:1236px;word-spacing:-3px;letter-spacing:2px">1.2<span class="l7">.1.<span class="w" style="width:26px"></span>Thu<span class="l8">ật t<span class="l7">oán</span></span></span></span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:959px;top:1443px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1158px;top:1444px;word-spacing:3px;letter-spacing:1px">Thuật toán được hiểu là sự đặc tả chính xác của một dãy các bước có thể</span><span class="a" style="left:959px;top:1587px;word-spacing:6px;letter-spacing:1px">được thực hiện một cách máy móc để giải quyết một vấn đề. Cần nhấn mạnh</span><span class="a" style="left:959px;top:1730px;letter-spacing:1px">rằng, mỗi thuật toán có một dữ liệu vào (Input) và dữ liệu ra (Output); khi thực</span><span class="a" style="left:959px;top:1873px;word-spacing:2px">hiện thuật toán (thực hiện các bước đã mô tả) , thuật toán cần cho ra các kiểu dữ</span><span class="a" style="left:959px;top:2016px;word-spacing:-2px">liệu ra tương ứng với <span class="w6"></span>các dữ liệu vào.[2]</span></div>
<div class="ff23" style="font-size:112px">
<span class="a" style="left:694px;top:2963px">1.2.2.</span></div>
<div class="ff16" style="font-size:117px">
<span class="a" style="left:1158px;top:2959px;word-spacing:-3px">Phân tích thuật toán</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:760px;top:3169px;word-spacing:-1px;letter-spacing:1px">1.2.2<span class="l6">.1.<span class="w" style="width:42px"></span>Tính <span class="l6">hiệu <span class="l7">quả củ<span class="l7">a thu<span class="l7">ật toán</span></span></span></span></span></span><span class="a" style="left:959px;top:3365px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1092px;top:3367px;word-spacing:-1px">Khi giải một vấn đề, chúng ta cần chọn trong số <span class="w6"></span>các thuật toán, một thuật toán</span><span class="a" style="left:1092px;top:3510px;word-spacing:-2px">mà chúng ta cho là “tốt” nhất. <span class="w6"></span>Cơ sở đánh chọn lựa <span class="w7"></span>thuật toán :</span></div>
<div class="ff14" style="font-size:70px">
<span class="a" style="left:761px;top:3722px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:893px;top:3706px;word-spacing:-2px">Thuật toán đơn giản, dễ hiểu, dễ <span class="w6"></span>cài đặt(dễ viết chương trình)</span></div>
<div class="ff14" style="font-size:59px">
<span class="a" style="left:761px;top:3923px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:893px;top:3896px;letter-spacing:1px">Thuật toán sử dụng tiết kiệm nhất các nguồn tài nguyên của máy tính và đặc biệt</span><span class="a" style="left:893px;top:4039px;word-spacing:-2px">chạy nhanh nhất có thể được.</span></div>
<div class="ff7" style="font-size:93px">
<span class="a" style="left:761px;top:4239px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1092px;top:4226px;word-spacing:-1px">Tính hiệu quả của thuật toán bao gồm 2 nhân tố cơ bản :</span></div>
<div class="ff14" style="font-size:70px">
<span class="a" style="left:761px;top:4442px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:893px;top:4426px;word-spacing:4px">Dung lượng không gian nhớ cần thiết để lưu giữ các dữ liệu vào, các kết quả tính</span><span class="a" style="left:893px;top:4569px;word-spacing:-2px">toán trung gian và các kết quả <span class="w6"></span>của thuật toán</span></div>
<div class="ff14" style="font-size:59px">
<span class="a" style="left:761px;top:4783px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:893px;top:4756px;word-spacing:-2px">Thời gian cần thiết để thực hiện thuật <span class="w6"></span>toán(hay thời gian chạy)</span></div>
<div class="ff7" style="font-size:79px">
<span class="a" style="left:3288px;top:4780px">&nbsp;</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:3313px;top:4756px">[3]</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:694px;top:4950px;word-spacing:-6px;letter-spacing:3px">1.<span class="l7">2.<span class="l6">2.<span class="l6">2.<span class="w" style="width:105px"></span>Đá<span class="l7">nh g<span class="l8">iá t<span class="l7">hờ<span class="l7">i gi<span class="l6">an t<span class="l7">hự<span class="l7">c hi<span class="l8">ện t<span class="l8">hu<span class="l7">ật t<span class="l6">oá<span class="l6">n</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:627px;top:5247px">&nbsp;</span></div>
<div class="ff21" style="font-size:99px">
<span class="a" style="left:2263px;top:5253px">5</span></div>
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&nbsp;
<div class="ff21" style="font-size:107px">
<span class="a" style="left:761px;top:526px;word-spacing:-9px;letter-spacing:6px">-<span class="w" style="width:293px"></span>T<span class="l7">h<span class="l6">ờ<span class="l6">i g<span class="l10">i<span class="l7">a<span class="l6">n c<span class="l10">h<span class="l6">ạ<span class="l6">y c<span class="l10">h<span class="l6">ư<span class="l7">ơ<span class="l6">n<span class="l6">g t<span class="l9">r<span class="l6">ì<span class="l7">n<span class="l6">h p<span class="l9">h<span class="l6">ụ t<span class="l9">h<span class="l6">u<span class="l6">ộ<span class="l7">c v<span class="l10">à<span class="l6">o c<span class="l10">á<span class="l6">c n<span class="l10">h<span class="l6">â<span class="l7">n t<span class="l9">ố c<span class="l10">h<span class="l6">í<span class="l6">n<span class="l6">h s<span class="l9">a<span class="l6">u<span class="l7">:</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></div>
<div class="ff14" style="font-size:70px">
<span class="a" style="left:761px;top:739px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1291px;top:722px;word-spacing:-2px">Các dữ liệu vào</span></div>
<div class="ff14" style="font-size:59px">
<span class="a" style="left:761px;top:939px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1291px;top:912px;word-spacing:-2px">Chương trình dịch để chuyển chương trình <span class="w6"></span>nguồn thành mã máy.</span></div>
<div class="ff14" style="font-size:59px">
<span class="a" style="left:1158px;top:1127px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1291px;top:1099px;word-spacing:3px">Tốc độ thực hiện của các phép toán của máy tính được sử dụng để chạy</span><span class="a" style="left:1291px;top:1242px;word-spacing:-3px">chương trình.</span></div>
<div class="ff7" style="font-size:79px">
<span class="a" style="left:959px;top:1454px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1092px;top:1429px;word-spacing:11px;letter-spacing:3px">Giả sử T(n) là thời gian thực hiện thuật toán và f(n) là hàm xác định</span><span class="a" style="left:1092px;top:1585px;word-spacing:4px">dương.T(n)=O(f(n)) nếu</span></div>
<div class="ff13" style="font-size:65px">
<span class="a" style="left:2061px;top:1606px">∃</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:2154px;top:1585px;word-spacing:1px;letter-spacing:1px">các hằng số dương c và n0 sao cho T(n)</span></div>
<div class="ff4" style="font-size:67px">
<span class="a" style="left:3781px;top:1597px">≤</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:3866px;top:1585px">c.g(n)</span><span class="a" style="left:1092px;top:1733px;word-spacing:-1px">với mọi n&gt;= n</span></div>
<div class="ff9" style="font-size:32px">
<span class="a" style="left:1662px;top:1793px">0</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1725px;top:1733px">.</span></div>
<div class="ff16" style="font-size:133px">
<span class="a" style="left:627px;top:1932px;word-spacing:-2px;letter-spacing:1px">1.3.<span class="w" style="width:19px"></span>Hạ tầng kh<span class="l7">óa công kh<span class="l6">ai (PKI)</span></span></span></div>
<div class="ff16" style="font-size:117px">
<span class="a" style="left:694px;top:2161px;word-spacing:-7px;letter-spacing:3px">1.<span class="l7">3.<span class="l7">1.<span class="w" style="width:27px"></span>PK<span class="l7">I là gì</span></span></span></span></div>
<div class="ff7" style="font-size:79px">
<span class="a" style="left:959px;top:2393px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1092px;top:2369px;word-spacing:2px">Để hiểu rõ về việc xây dựng cơ PKI và vần đề cấp phát chứng thực số có vai</span><span class="a" style="left:959px;top:2512px;word-spacing:-1px;letter-spacing:1px">trò và ứng <span class="w6"></span>dụng như thế nào trong thương mại điên tử. Chúng ta <span class="w6"></span>sẽ đi <span class="w6"></span>phân tích</span><span class="a" style="left:959px;top:2655px;word-spacing:-2px">từng khía cạnh xung quanh PKI.</span></div>
<div class="ff7" style="font-size:93px">
<span class="a" style="left:959px;top:2855px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1092px;top:2842px;word-spacing:-2px">Trước tiên chúng hiểu thế nào là PKI <span class="w7"></span>và tính cấp thiết của PKI hiện <span class="w6"></span>nay :</span></div>
<div class="ff14" style="font-size:59px">
<span class="a" style="left:1158px;top:3060px"></span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:1291px;top:3031px">PKI</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1484px;top:3032px;word-spacing:5px;letter-spacing:1px">: viết tắt của Public Key Infrastructure tức là hạ tầng cơ sở khóa</span><span class="a" style="left:1158px;top:3175px;word-spacing:8px">công khai.</span></div>
<div class="ff16" style="font-size:117px">
<span class="a" style="left:1568px;top:3167px">&nbsp;</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1605px;top:3175px;word-spacing:6px;letter-spacing:1px">Là một cơ chế để cho một bên thứ 3 (thường là nhà cung cấp</span><span class="a" style="left:1158px;top:3318px;word-spacing:3px;letter-spacing:1px">chứng thực số) cung cấp và xác thực định danh các bên tham gia vào quá</span><span class="a" style="left:1158px;top:3461px;word-spacing:1px;letter-spacing:1px">trình trao đổi thông tin.</span></div>
<div class="ff21" style="font-size:115px">
<span class="a" style="left:2086px;top:3454px">&nbsp;</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:2122px;top:3461px;word-spacing:4px;letter-spacing:1px">Cơ chế này cũng cho phép gán cho mỗi người sử</span><span class="a" style="left:1158px;top:3604px;word-spacing:-2px">dụng trong hệ thống một <span class="w6"></span>cặp khóa công khai/khóa bí mật.</span></div>
<div class="ff14" style="font-size:59px">
<span class="a" style="left:1158px;top:3819px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1291px;top:3791px;word-spacing:4px">Trong kỷ nguyên bùng nổ của công nghệ thông tin, mọi giao dịch từ xa</span><span class="a" style="left:1158px;top:3934px">có thể thông qua internet. Tuy nhiên, mặt khác khó mà bảo đảm rằng những</span><span class="a" style="left:1158px;top:4077px;word-spacing:1px">giao dịch trên Internet luôn an toàn. Cơ sở hạ tầng khóa công khai (PKI) đã</span><span class="a" style="left:1158px;top:4220px;word-spacing:1px;letter-spacing:1px">đáp ứng những yêu cầu cấp thiết đó. Dựa trên cách sử dụng của chìa khóa</span><span class="a" style="left:1158px;top:4363px;word-spacing:3px;letter-spacing:1px">mật mã công cộng và chữ ký điện tử, một PKI chính là bộ khung của các</span><span class="a" style="left:1158px;top:4506px;word-spacing:6px;letter-spacing:1px">chính sách, dịch vụ và phần mềm mã hóa, đáp ứng nhu cầu bảo mật của</span><span class="a" style="left:1158px;top:4649px;word-spacing:-1px">người sử dụng.</span></div>
<div class="ff16" style="font-size:117px">
<span class="a" style="left:694px;top:4844px;word-spacing:-2px;letter-spacing:1px">1.3.<span class="l6">2.<span class="w" style="width:31px"></span>Cở sở hạ t<span class="l7">ầng kh<span class="l7">óa côn<span class="l6">g khai</span></span></span></span></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:627px;top:5247px">&nbsp;</span></div>
<div class="ff21" style="font-size:99px">
<span class="a" style="left:2263px;top:5253px">6</span></div>
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<span class="a" style="left:1423px;top:2241px;word-spacing:-2px">Hình 1.4 : Mô hình xây <span class="w6"></span>dựng PKI cơ bản</span></div>
<div class="ff7" style="font-size:79px">
<span class="a" style="left:826px;top:2466px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:959px;top:2441px;word-spacing:4px;letter-spacing:1px">PKI cung cấp một cặp chìa khóa, trong đó có một chìa là chìa khóa công khai</span><span class="a" style="left:959px;top:2584px;word-spacing:3px">(Public key) để có thể sử dụng dịch vụ, chìa còn lại là chìa khóa bí mật (Private</span><span class="a" style="left:959px;top:2727px;word-spacing:1px">key) mà người sử dụng phải giữ bí mật. Hai chìa khóa này có liên quan mật thiết</span><span class="a" style="left:959px;top:2870px;word-spacing:4px">đến nhau, sao cho một thông điệp được mã hóa bởi một chìa khóa mật mã công</span><span class="a" style="left:959px;top:3013px;word-spacing:-2px">khai thì chỉ giải mã được bởi <span class="w6"></span>một chìa khóa bí mật tương <span class="w6"></span>ứng.</span></div>
<div class="ff7" style="font-size:93px">
<span class="a" style="left:826px;top:3213px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:959px;top:3200px;word-spacing:-1px">Ví dụ về mô hình xử dụng xác thực :</span><span class="a" style="left:959px;top:3390px;word-spacing:1px">Giả sử có 2 người dùng Bob và Alice muốn chuyển thư điện tử cho nhau để đảm</span><span class="a" style="left:935px;top:3533px;word-spacing:-1px">&nbsp;bảo tính xác thực và bảo mật họ dùng 1 phần mềm PKI</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:1394px;top:3981px;word-spacing:-29px;letter-spacing:29px">H<span class="l" style="margin-left:-30px">à<span class="l" style="margin-left:-29px">n<span class="l" style="margin-left:-30px">h <span class="l" style="margin-left:-29px">đ<span class="l" style="margin-left:-30px">ộ<span class="l" style="margin-left:-29px">n<span class="l" style="margin-left:-30px">g<span class="w" style="width:829px"></span>T<span class="l" style="margin-left:-29px">r<span class="l" style="margin-left:-29px">ạ<span class="l" style="margin-left:-29px">n<span class="l" style="margin-left:-30px">g <span class="l" style="margin-left:-29px">t<span class="l" style="margin-left:-29px">h<span class="l" style="margin-left:-30px">á<span class="l" style="margin-left:-29px">i <span class="l" style="margin-left:-29px">c<span class="l" style="margin-left:-30px">ủ<span class="l" style="margin-left:-30px">a <span class="l" style="margin-left:-29px">h<span class="l" style="margin-left:-30px">ệ <span class="l" style="margin-left:-29px">t<span class="l" style="margin-left:-29px">h<span class="l" style="margin-left:-30px">ố<span class="l" style="margin-left:-29px">n<span class="l" style="margin-left:-30px">g <span class="l" style="margin-left:-29px">P<span class="l" style="margin-left:-30px">K<span class="l" style="margin-left:-29px">I</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:824px;top:4202px;word-spacing:5px;letter-spacing:2px">Bob muốn chuyển một thư điện tử đến</span><span class="a" style="left:824px;top:4345px;word-spacing:11px;letter-spacing:2px">cho Alice, với yêu cầu rằng giao dịch</span><span class="a" style="left:800px;top:4488px;word-spacing:3px;letter-spacing:1px">&nbsp;phải chứng minh được chính anh đã gởi</span><span class="a" style="left:824px;top:4631px;word-spacing:1px;letter-spacing:1px">nó đi và nội dung bức thư không bị thay</span><span class="a" style="left:824px;top:4774px">đổi.</span><span class="a" style="left:2498px;top:4202px;word-spacing:5px;letter-spacing:1px">Phần mềm PKI dùng chìa khóa cá nhân</span><span class="a" style="left:2498px;top:4345px;word-spacing:5px;letter-spacing:2px">của Bob tạo ra một chữ ký điện tử cho</span><span class="a" style="left:2474px;top:4488px;word-spacing:-1px">&nbsp;bức thư</span><span class="a" style="left:824px;top:4994px;word-spacing:6px">Bob <span class="l6">muốn <span class="l7">chắc <span class="l7">chắn <span class="l8">rằng <span class="l7">không <span class="l7">ai <span class="l6">ngoài <span class="w" style="width:49px"></span>Phần mềm PKI của <span class="w6"></span>Bob dùng chìa khóa</span></span></span></span></span></span></span></span></div>
<div class="ff21" style="font-size:99px">
<span class="a" style="left:2263px;top:5253px">7</span></div>
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<span class="a" style="left:824px;top:583px;word-spacing:-8px;letter-spacing:14px">A<span class="l" style="margin-left:-14px">l<span class="l" style="margin-left:-14px">i<span class="l" style="margin-left:-15px">c<span class="l" style="margin-left:-14px">e <span class="l" style="margin-left:-21px">đ<span class="l" style="margin-left:-14px">ọ<span class="l" style="margin-left:-14px">c <span class="l" style="margin-left:-20px">đ<span class="l" style="margin-left:-15px">ư<span class="l" style="margin-left:-14px">ợ<span class="l" style="margin-left:-14px">c <span class="l" style="margin-left:-20px">b<span class="l" style="margin-left:-14px">ứ<span class="l" style="margin-left:-15px">c <span class="l" style="margin-left:-20px">t<span class="l" style="margin-left:-15px">h<span class="l" style="margin-left:-14px">ư <span class="l" style="margin-left:-19px">n<span class="l" style="margin-left:-15px">à<span class="l" style="margin-left:-14px">y<span class="w" style="width:594px"></span>c<span class="l" style="margin-left:-14px">ô<span class="l" style="margin-left:-14px">n<span class="l" style="margin-left:-14px">g c<span class="l" style="margin-left:-13px">ộ<span class="l" style="margin-left:-14px">n<span class="l" style="margin-left:-15px">g c<span class="l" style="margin-left:-13px">ủ<span class="l" style="margin-left:-14px">a A<span class="l" style="margin-left:-13px">l<span class="l" style="margin-left:-15px">i<span class="l" style="margin-left:-14px">c<span class="l" style="margin-left:-14px">e đ<span class="l" style="margin-left:-14px">ể m<span class="l" style="margin-left:-13px">ã h<span class="l" style="margin-left:-13px">ó<span class="l" style="margin-left:-15px">a t<span class="l" style="margin-left:-13px">h<span class="l" style="margin-left:-14px">ô<span class="l" style="margin-left:-14px">n<span class="l" style="margin-left:-14px">g</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span><span class="a" style="left:2498px;top:726px;word-spacing:-1px">điệp của Bob.</span><span class="a" style="left:824px;top:945px;word-spacing:-8px;letter-spacing:10px">A<span class="l10">l<span class="l10">i<span class="l11">c<span class="l10">e <span class="l" style="margin-left:-13px">m<span class="l10">u<span class="l10">ố<span class="l10">n <span class="l12">đ<span class="l10">ọ<span class="l11">c <span class="l12">t<span class="l10">h<span class="l11">ư <span class="l12">d<span class="l10">o <span class="l12">B<span class="l10">o<span class="l10">b <span class="l12">g<span class="l10">ở<span class="l10">i<span class="w" style="width:448px"></span>P<span class="l11">h<span class="l10">ầ<span class="l10">n m<span class="l10">ề<span class="l11">m P<span class="l12">K<span class="l10">I d<span class="l10">ù<span class="l10">n<span class="l10">g c<span class="l11">h<span class="l10">ì<span class="l11">a k<span class="l10">h<span class="l10">ó<span class="l11">a c<span class="l11">á n<span class="l10">h<span class="l11">â<span class="l10">n</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span><span class="a" style="left:2498px;top:1088px;word-spacing:-2px">của Alice để để giải mã <span class="w6"></span>thông điệp.</span><span class="a" style="left:824px;top:1309px;word-spacing:1px;letter-spacing:1px">Alice muốn kiểm chứng rằng chính Bob</span><span class="a" style="left:824px;top:1451px;word-spacing:11px;letter-spacing:4px">đã gởi đi thông điệp đó và nội dung</span><span class="a" style="left:824px;top:1594px;word-spacing:-1px">thông điệp không bị chỉnh sửa.</span><span class="a" style="left:2498px;top:1309px">Phần mềm PKI của Alice dùng chìa khóa</span><span class="a" style="left:2498px;top:1451px;word-spacing:3px;letter-spacing:2px">công cộng của Bob để kiểm chứng chữ</span><span class="a" style="left:2498px;top:1594px;word-spacing:-1px">ký điện tử của anh ta.</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:1839px;top:1813px;word-spacing:-2px">Bảng 1.5 : Mô hình sử <span class="w6"></span>dụng xác thực</span></div>
<div class="ff23" style="font-size:128px">
<span class="a" style="left:627px;top:2210px">1.4.</span></div>
<div class="ff16" style="font-size:133px">
<span class="a" style="left:893px;top:2205px">Một vài kiến trúc và công nghệ PKI hiện hành</span></div>
<div class="ff16" style="font-size:117px">
<span class="a" style="left:694px;top:2437px;word-spacing:-5px;letter-spacing:2px">1.4<span class="l7">.1.<span class="w" style="width:26px"></span>Một s<span class="l7">ố ứng d<span class="l6">ụn<span class="l6">g</span></span></span></span></span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:761px;top:2645px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:959px;top:2646px">Mục tiêu chính của PKI là cung cấp khóa công khai và xác định mối liên hệ giữa</span><span class="a" style="left:893px;top:2789px;letter-spacing:1px">khóa và định dạng người dùng. Nhờ vậy người dùng có thể sử dụng trong một số</span><span class="a" style="left:893px;top:2932px;word-spacing:-1px">ứng dụng như:</span></div>
<div class="ff12" style="font-size:29px">
<span class="a" style="left:1025px;top:3165px;color:#000000;-ms-filter: " progid:dximagetransform.microsoft.alpha(opacity="50)&quot;;filter:" alpha(opacity="50);opacity:" 0.50"=""></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1158px;top:3128px;word-spacing:-2px">Mã hoá Email hoặc xác thực người <span class="w6"></span>gửi Email (OpenPGP hay S/MIME).</span></div>
<div class="ff12" style="font-size:29px">
<span class="a" style="left:1025px;top:3365px;color:#000000;-ms-filter: " progid:dximagetransform.microsoft.alpha(opacity="50)&quot;;filter:" alpha(opacity="50);opacity:" 0.50"=""></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1158px;top:3328px;word-spacing:5px;letter-spacing:1px">Mã hóa hoặc nhận thực văn bản (Các tiêu chuẩn Chữ ký XML* hoặc mã</span><span class="a" style="left:1158px;top:3471px;word-spacing:-1px">hoá XML* khi văn bản được thể hiện dưới dạng XML).</span></div>
<div class="ff12" style="font-size:29px">
<span class="a" style="left:1025px;top:3704px;color:#000000;-ms-filter: " progid:dximagetransform.microsoft.alpha(opacity="50)&quot;;filter:" alpha(opacity="50);opacity:" 0.50"=""></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1158px;top:3667px;word-spacing:11px;letter-spacing:4px">Xác thực người dùng ứng dụng (Đăng nhập bằng thẻ thông minh -</span><span class="a" style="left:1158px;top:3810px;word-spacing:-2px">smartcard, nhận thực người dùng trong SSL).</span></div>
<div class="ff12" style="font-size:29px">
<span class="a" style="left:1025px;top:4044px;color:#000000;-ms-filter: " progid:dximagetransform.microsoft.alpha(opacity="50)&quot;;filter:" alpha(opacity="50);opacity:" 0.50"=""></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1158px;top:4006px;word-spacing:7px;letter-spacing:2px">Các giao thức truyền thông an toàn dùng kỹ thuật Bootstrapping (IKE,</span><span class="a" style="left:1158px;top:4149px;word-spacing:3px;letter-spacing:2px">SSL): trao đổi khóa bằng khóa bất đối xứng, còn mã hóa bằng khóa đối</span><span class="a" style="left:1158px;top:4292px">xứng.</span></div>
<div class="ff16" style="font-size:117px">
<span class="a" style="left:694px;top:4487px;letter-spacing:1px">1.4.<span class="l6">2.<span class="w" style="width:31px"></span>Một <span class="l6">số hệ <span class="l8">thốn<span class="l6">g PKI</span></span></span></span></span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:761px;top:4694px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:959px;top:4695px">Dưới đây là danh sách một số hệ thống PKI, trong đó một số nhà cung cấp chứng</span><span class="a" style="left:893px;top:4838px;word-spacing:6px;letter-spacing:1px">thực số hàng đầu (ví dụ VeriSign) không được liệt kê vì các phần mềm của họ</span><span class="a" style="left:893px;top:4981px;word-spacing:-1px">không được công bố công khai :</span><span class="a" style="left:627px;top:5247px">&nbsp;</span></div>
<div class="ff21" style="font-size:99px">
<span class="a" style="left:2263px;top:5253px">8</span></div>
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<span class="a" style="left:893px;top:535px;word-spacing:-1px">Hệ thống quản lý chứng thực Red Hat</span></div>
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<span class="a" style="left:1158px;top:734px;word-spacing:-2px">Computer Associate eTrust PKI</span></div>
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<span class="a" style="left:893px;top:933px">Microsoft</span></div>
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<span class="a" style="left:893px;top:1133px;word-spacing:-1px">OpenCA (Một mô hình PKI mã nguồn mở)</span></div>
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<span class="a" style="left:893px;top:1332px;word-spacing:-4px">RSA Security</span></div>
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<span class="a" style="left:893px;top:1532px">IDX-PKI</span></div>
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<span class="a" style="left:893px;top:1731px;word-spacing:-3px">Simple CA</span></div>
<div class="ff16" style="font-size:133px">
<span class="a" style="left:627px;top:1929px;letter-spacing:1px">1.5.<span class="w" style="width:19px"></span>Mục đí<span class="l6">ch của <span class="l6">đề tài</span></span></span></div>
<div class="ff7" style="font-size:79px">
<span class="a" style="left:694px;top:2183px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:826px;top:2159px;word-spacing:3px">Một vài năm trở lại đây PKI là 1 chủ đề nóng đối với các doanh nghiệp lớn. Ở Việt</span><span class="a" style="left:802px;top:2302px;word-spacing:3px">&nbsp;Nam đây vấn là một đề tài khá mới mẻ. Do vậy tìm hiểu và xây dựng hạ tầng cơ sở&nbsp;</span><span class="a" style="left:826px;top:2445px">xác thực khóa công khai(PKI) là một cách tiếp cận cho một nền tảng mới. Từ đó nêu</span><span class="a" style="left:826px;top:2588px;word-spacing:-1px">rõ vai trò và ứng dụng của hạ tầng khóa công khai trong thương mại điện tử.</span></div>
<div class="ff7" style="font-size:93px">
<span class="a" style="left:694px;top:2788px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:826px;top:2775px;word-spacing:5px;letter-spacing:1px">Tìm hiểu về các thuật toán(sinh số ngẫu nhiên trong việc tạo khóa, hàm băm, mã</span><span class="a" style="left:826px;top:2920px;word-spacing:-1px">hóa, tạo chữ ký số...)</span></div>
<div class="ff16" style="font-size:133px">
<span class="a" style="left:627px;top:3677px;word-spacing:-2px;letter-spacing:2px">1.6.<span class="w" style="width:15px"></span>Đặt v<span class="l7">ần đ<span class="l6">ề ?</span></span></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:694px;top:3907px;word-spacing:2px;letter-spacing:3px">-<span class="w" style="width:97px"></span>Để xâ<span class="l7">y dựn<span class="l7">g một cơ sở h<span class="l7">ạ tần<span class="l7">g chú<span class="l7">ng ta ph<span class="l8">ải gi<span class="l8">ải qu<span class="l7">yế<span class="l7">t sơ bộ nhữ<span class="l8">ng vấ<span class="l7">n đề sau</span></span></span></span></span></span></span></span></span></span></span></span><span class="a" style="left:826px;top:4050px;word-spacing:-1px">đây :</span></div>
<div class="ff14" style="font-size:70px">
<span class="a" style="left:761px;top:4263px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1025px;top:4247px;word-spacing:-2px">Làm sao để cấp phát khóa <span class="w7"></span>công khai và khóa bí mật cho <span class="w6"></span>từng người.</span></div>
<div class="ff14" style="font-size:70px">
<span class="a" style="left:761px;top:4462px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1025px;top:4446px;word-spacing:-1px">Vấn đề đăng ký khóa công khai với một CA</span></div>
<div class="ff14" style="font-size:70px">
<span class="a" style="left:761px;top:4662px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1025px;top:4645px;word-spacing:-2px">Vấn đề thu hồi/cấp phát lại khóa <span class="w6"></span>công khai</span></div>
<div class="ff14" style="font-size:59px">
<span class="a" style="left:761px;top:4863px"></span></div>
<div class="ff7" style="font-size:93px">
<span class="a" style="left:896px;top:4849px">&nbsp;</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1056px;top:4835px;word-spacing:-1px">Vấn đề kiểm chứng khóa công khai</span><span class="a" style="left:627px;top:5247px">&nbsp;</span></div>
<div class="ff21" style="font-size:99px">
<span class="a" style="left:2263px;top:5253px">9</span></div>
</div>
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&nbsp;
<div class="ff16" style="font-size:150px">
<span class="a" style="left:689px;top:578px">Chương 2 : Xây dựng hạ tầng khóa công khai(PKI), vấn đề</span><span class="a" style="left:677px;top:776px">cấp phát chứng thực số và ứng dụng trong thương mại điện</span><span class="a" style="left:2298px;top:974px">tử&nbsp;</span></div>
<div class="ff16" style="font-size:133px">
<span class="a" style="left:627px;top:1455px;letter-spacing:1px">2.1.<span class="w" style="width:19px"></span>Hàm bă<span class="l6">m mật m<span class="l6">ã học</span></span></span></div>
<div class="ff16" style="font-size:117px">
<span class="a" style="left:694px;top:1684px;word-spacing:-8px;letter-spacing:3px">2.<span class="l7">1.<span class="l7">1.<span class="w" style="width:27px"></span>Hà<span class="l8">m băm</span></span></span></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:959px;top:1892px;word-spacing:-17px;letter-spacing:24px">-<span class="w" style="width:143px"></span>H<span class="l" style="margin-left:-25px">à<span class="l" style="margin-left:-24px">m <span class="l" style="margin-left:-23px">b<span class="l" style="margin-left:-24px">ă<span class="l" style="margin-left:-24px">m <span class="l" style="margin-left:-23px">(</span></span></span></span></span></span></span><span class="a" style="left:1606px;top:1892px;word-spacing:7px"><a rel="nofollow" href="http://vi.wikipedia.org/wiki/Ti%E1%BA%BFng_Anh" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvd2lraS9UaSVFMSVCQSVCRm5nX0FuaA==">tiếng Anh</a></span><span class="a" style="left:1995px;top:1892px">:</span></div>
<div class="ff8" style="font-size:106px">
<span class="a" style="left:2054px;top:1893px;word-spacing:6px">hash function</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:2581px;top:1892px;word-spacing:3px;letter-spacing:1px">) là hàm sinh ra các giá trị băm tương</span><span class="a" style="left:959px;top:2035px;word-spacing:1px">ứng với mỗi khối dữ liệu (có thể là một chuỗi kí tự, một đoạn tin nhắn...). Giá trị</span><span class="a" style="left:935px;top:2178px;word-spacing:7px;letter-spacing:1px">&nbsp;băm đóng vai trò gần như một khóa để phân biệt các khối dữ liệu, tuy nhiên,</span><span class="a" style="left:959px;top:2321px;word-spacing:2px">người ta chấp nhận hiện tượng trùng khóa hay còn gọi là</span><span class="a" style="left:3190px;top:2321px;word-spacing:3px"><a rel="nofollow" href="http://vi.wikipedia.org/w/index.php?title=%C4%90%E1%BB%A5ng_%C4%91%E1%BB%99_b%C4%83m&amp;action=edit&amp;redlink=1" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvdy9pbmRleC5waHA/dGl0bGU9JUM0JTkwJUUxJUJCJUE1bmdfJUM0JTkxJUUxJUJCJTk5X2IlQzQlODNtJmFjdGlvbj1lZGl0JnJlZGxpbms9MQ==">đụng độ</a></span><span class="a" style="left:3532px;top:2321px;word-spacing:1px">và cố gắng cải</span><span class="a" style="left:959px;top:2464px;word-spacing:3px">thiện giải thuật để giảm thiểu sự</span><span class="a" style="left:2247px;top:2464px;word-spacing:4px"><a rel="nofollow" href="http://vi.wikipedia.org/w/index.php?title=%C4%90%E1%BB%A5ng_%C4%91%E1%BB%99_b%C4%83m&amp;action=edit&amp;redlink=1" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvdy9pbmRleC5waHA/dGl0bGU9JUM0JTkwJUUxJUJCJUE1bmdfJUM0JTkxJUUxJUJCJTk5X2IlQzQlODNtJmFjdGlvbj1lZGl0JnJlZGxpbms9MQ==">đụng độ</a></span><span class="a" style="left:2591px;top:2464px;word-spacing:3px">đó. Hàm băm thường được dùng trong</span><span class="a" style="left:935px;top:2607px;word-spacing:8px"><a rel="nofollow" href="http://vi.wikipedia.org/w/index.php?title=B%E1%BA%A3ng_b%C4%83m&amp;action=edit&amp;redlink=1" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvdy9pbmRleC5waHA/dGl0bGU9QiVFMSVCQSVBM25nX2IlQzQlODNtJmFjdGlvbj1lZGl0JnJlZGxpbms9MQ==">&nbsp;bảng băm</a></span><span class="a" style="left:1378px;top:2607px;word-spacing:4px;letter-spacing:1px">nhằm giảm chi phí tính toán khi tìm một khối dữ liệu trong một tập</span><span class="a" style="left:959px;top:2750px;word-spacing:1px">hợp (nhờ việc so sánh các giá trị băm nhanh hơn việc so sánh những</span></div>
<div class="ff8" style="font-size:106px">
<span class="a" style="left:3632px;top:2751px;word-spacing:1px">khối dữ liệu</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:959px;top:2893px;word-spacing:-2px">có kích thước lớn).</span></div>
<div class="ff16" style="font-size:117px">
<span class="a" style="left:694px;top:3087px;letter-spacing:1px">2.1.<span class="l6">2.<span class="w" style="width:31px"></span>Hàm <span class="l6">băm m<span class="l6">ật m<span class="l6">ã học</span></span></span></span></span></div>
<div class="ff21" style="font-size:99px">
<span class="a" style="left:826px;top:3303px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="g" style="top:3296px"><span class="a" style="left:959px;word-spacing:3px">Trong ngành</span><span class="a" style="left:1485px;word-spacing:3px"><a rel="nofollow" href="http://vi.wikipedia.org/wiki/M%E1%BA%ADt_m%C3%A3_h%E1%BB%8Dc" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvd2lraS9NJUUxJUJBJUFEdF9tJUMzJUEzX2glRTElQkIlOERj">mật mã học</a></span><span class="a" style="left:1942px;word-spacing:4px">, một hàm băm mật mã học (</span><span class="a" style="left:3078px;word-spacing:3px"><a rel="nofollow" href="http://vi.wikipedia.org/wiki/Ti%E1%BA%BFng_Anh" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvd2lraS9UaSVFMSVCQSVCRm5nX0FuaA==">tiếng Anh</a></span><span class="a" style="left:3463px">:</span></span>
</div>
<div class="ff8" style="font-size:106px">
<span class="a" style="left:3518px;top:3297px">Cryptographic</span><span class="a" style="left:959px;top:3440px;word-spacing:7px">hash function</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1487px;top:3439px;word-spacing:2px;letter-spacing:2px">) là một</span><span class="a" style="left:1839px;top:3439px;word-spacing:2px;letter-spacing:1px"><a rel="nofollow" href="http://vi.wikipedia.org/wiki/H%C3%A0m_b%C4%83m" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvd2lraS9IJUMzJUEwbV9iJUM0JTgzbQ==">hàm băm</a></span><span class="a" style="left:2235px;top:3439px;word-spacing:4px;letter-spacing:1px">với một số tính chất bảo mật nhất định để phù</span><span class="a" style="left:959px;top:3582px;word-spacing:4px;letter-spacing:1px">hợp việc sử dụng trong nhiều ứng dụng</span><span class="a" style="left:2555px;top:3582px;word-spacing:3px;letter-spacing:1px"><a rel="nofollow" href="http://vi.wikipedia.org/w/index.php?title=B%E1%BA%A3o_m%E1%BA%ADt_th%C3%B4ng_tin&amp;action=edit&amp;redlink=1" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvdy9pbmRleC5waHA/dGl0bGU9QiVFMSVCQSVBM29fbSVFMSVCQSVBRHRfdGglQzMlQjRuZ190aW4mYWN0aW9uPWVkaXQmcmVkbGluaz0x">&nbsp;bảo mật thông tin</a></span><span class="a" style="left:3320px;top:3582px;word-spacing:4px;letter-spacing:1px">đa dạng, chẳng hạn</span><span class="g" style="top:3725px"><span class="a" style="left:959px">như</span><span class="a" style="left:1148px;word-spacing:7px;letter-spacing:1px"><a rel="nofollow" href="http://vi.wikipedia.org/w/index.php?title=Ch%E1%BB%A9ng_th%E1%BB%B1c&amp;action=edit&amp;redlink=1" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvdy9pbmRleC5waHA/dGl0bGU9Q2glRTElQkIlQTluZ190aCVFMSVCQiVCMWMmYWN0aW9uPWVkaXQmcmVkbGluaz0x">chứng thực</a></span><span class="a" style="left:1640px;word-spacing:6px;letter-spacing:1px">(authentication) và kiểm tra</span><span class="a" style="left:2797px;word-spacing:5px;letter-spacing:2px"><a rel="nofollow" href="http://vi.wikipedia.org/w/index.php?title=T%C3%ADnh_nguy%C3%AAn_v%E1%BA%B9n_c%E1%BB%A7a_th%C3%B4ng_%C4%91i%E1%BB%87p&amp;action=edit&amp;redlink=1" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvdy9pbmRleC5waHA/dGl0bGU9VCVDMyVBRG5oX25ndXklQzMlQUFuX3YlRTElQkElQjluX2MlRTElQkIlQTdhX3RoJUMzJUI0bmdfJUM0JTkxaSVFMSVCQiU4N3AmYWN0aW9uPWVkaXQmcmVkbGluaz0x">tính nguyên vẹn của thông điệp</a></span><span class="a" style="left:4092px">&nbsp;</span></span>
<span class="a" style="left:959px;top:3868px">(</span></div>
<div class="ff8" style="font-size:106px">
<span class="a" style="left:991px;top:3869px">message integrity</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1666px;top:3868px;word-spacing:1px">). Một hàm băm nhận đầu vào là một</span><span class="a" style="left:3132px;top:3868px;word-spacing:1px"><a rel="nofollow" href="http://vi.wikipedia.org/w/index.php?title=X%C3%A2u_k%C3%BD_t%E1%BB%B1&amp;action=edit&amp;redlink=1" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvdy9pbmRleC5waHA/dGl0bGU9WCVDMyVBMnVfayVDMyVCRF90JUUxJUJCJUIxJmFjdGlvbj1lZGl0JnJlZGxpbms9MQ==">xâu ký tự</a></span><span class="a" style="left:3524px;top:3868px;word-spacing:1px">dài (hay</span></div>
<div class="ff8" style="font-size:106px">
<span class="a" style="left:3865px;top:3869px">thông&nbsp;</span><span class="a" style="left:959px;top:4011px">điệp</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1124px;top:4011px">) có độ dài tùy ý và tạo ra kết quả là một xâu ký tự có độ dài cố định, đôi khi</span><span class="g" style="top:4154px"><span class="a" style="left:959px;word-spacing:10px;letter-spacing:4px">được gọi là</span></span>
</div>
<div class="ff8" style="font-size:106px">
<span class="g" style="top:4154px"><span class="a" style="left:1509px;word-spacing:13px;letter-spacing:3px"><a rel="nofollow" href="http://vi.wikipedia.org/w/index.php?title=T%C3%B3m_t%E1%BA%AFt_th%C3%B4ng_%C4%91i%E1%BB%87p&amp;action=edit&amp;redlink=1" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvdy9pbmRleC5waHA/dGl0bGU9VCVDMyVCM21fdCVFMSVCQSVBRnRfdGglQzMlQjRuZ18lQzQlOTFpJUUxJUJCJTg3cCZhY3Rpb249ZWRpdCZyZWRsaW5rPTE=">tóm tắt thông điệp</a></span></span>
</div>
<div class="ff21" style="font-size:107px">
<span class="g" style="top:4154px"><span class="a" style="left:2358px">(</span></span>
</div>
<div class="ff8" style="font-size:106px">
<span class="g" style="top:4154px"><span class="a" style="left:2390px;word-spacing:17px;letter-spacing:1px">messag<span class="l6">e <span class="w12"></span>diges<span class="l6">t&nbsp;</span></span></span></span>
</div>
<div class="ff21" style="font-size:107px">
<span class="g" style="top:4154px"><span class="a" style="left:2999px;word-spacing:10px;letter-spacing:4px">) hoặc</span></span>
</div>
<div class="ff8" style="font-size:106px">
<span class="g" style="top:4154px"><span class="a" style="left:3322px;word-spacing:10px;letter-spacing:5px"><a rel="nofollow" href="http://vi.wikipedia.org/wiki/Ch%E1%BB%AF_k%C3%BD_s%E1%BB%91" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvd2lraS9DaCVFMSVCQiVBRl9rJUMzJUJEX3MlRTElQkIlOTE=">chữ ký số&nbsp;</a></span></span>
</div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:3745px;top:4154px"><a rel="nofollow" href="http://vi.wikipedia.org/wiki/Ch%E1%BB%AF_k%C3%BD_s%E1%BB%91" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvd2lraS9DaCVFMSVCQiVBRl9rJUMzJUJEX3MlRTElQkIlOTE=">&nbsp;</a></span><span class="a" style="left:3801px;top:4154px">(</span></div>
<div class="ff8" style="font-size:106px">
<span class="a" style="left:3833px;top:4154px">digital&nbsp;</span><span class="a" style="left:935px;top:4297px">&nbsp;fingerprint&nbsp;</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1374px;top:4297px">).[4]</span></div>
<div class="ff16" style="font-size:117px">
<span class="a" style="left:694px;top:4491px;word-spacing:-3px;letter-spacing:1px">2.1.<span class="l6">3.<span class="w" style="width:31px"></span>Đảm bả<span class="l6">o tính to<span class="l7">àn vẹn dữ li<span class="l6">ệu</span></span></span></span></span></div>
<div class="ff21" style="font-size:99px">
<span class="a" style="left:826px;top:4706px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:959px;top:4700px;word-spacing:4px;letter-spacing:1px">Hàm băm mậ<span class="l6">t mã học là hàm bam và <span class="w" style="width:28px"></span>có tính chấ<span class="l6">t là hàm 1 chiều<span class="l6">. Từ khối dữ</span></span></span></span><span class="a" style="left:959px;top:4843px;word-spacing:2px">liệu hay giá trị băm đầu vào chỉ có thể đưa ra 1 giá trị băm duy nhất. Như chúng</span></div>
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<span class="a" style="left:2241px;top:5253px">11</span></div>
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&nbsp;
<div class="ff21" style="font-size:107px">
<span class="a" style="left:959px;top:526px;word-spacing:-1px">ta đã biết đối với tính chất của <span class="w6"></span>hàm 1 chiều. Một người nào đó <span class="w6"></span>dù bắt được giá trị</span><span class="a" style="left:935px;top:669px;word-spacing:-1px">&nbsp;băm họ cũng không thể suy ngược lại giá trị, đoạn tin nhắn băm khởi điểm.</span></div>
<div class="ff21" style="font-size:99px">
<span class="a" style="left:826px;top:863px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:959px;top:856px;word-spacing:-2px">Hàm băm thường được dùng trong</span><span class="a" style="left:2291px;top:856px;word-spacing:-1px"><a rel="nofollow" href="http://vi.wikipedia.org/w/index.php?title=B%E1%BA%A3ng_b%C4%83m&amp;action=edit&amp;redlink=1" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvdy9pbmRleC5waHA/dGl0bGU9QiVFMSVCQSVBM25nX2IlQzQlODNtJmFjdGlvbj1lZGl0JnJlZGxpbms9MQ==">&nbsp;bảng băm</a></span><span class="a" style="left:2714px;top:856px;word-spacing:-1px">nhằm giảm chi phí tính toán khi tìm</span><span class="a" style="left:959px;top:999px;letter-spacing:1px">một khối dữ liệu trong một tập hợp. Giá trị <span class="w6"></span>băm đóng vai trò gần như <span class="w6"></span>một khóa</span><span class="a" style="left:959px;top:1142px;word-spacing:-2px">để phân biệt các khối dữ <span class="w6"></span>liệu</span></div>
<div class="ff21" style="font-size:99px">
<span class="a" style="left:826px;top:1336px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:959px;top:1329px;word-spacing:-1px">Giá trị đầu vào(tin nhắn, dữ liệu...) bị thay đổi tương ứng <span class="w6"></span>giá trị băm cũng bị thay</span><span class="a" style="left:959px;top:1472px;word-spacing:1px;letter-spacing:1px">đổi. Do vậy nếu 1 kẻ tấn công phá hoại, chỉnh sửa dữ liệu thì server có thể biết</span><span class="a" style="left:959px;top:1615px;word-spacing:-2px">ngay lập tức.</span></div>
<div class="ff16" style="font-size:117px">
<span class="a" style="left:694px;top:1810px;word-spacing:-2px;letter-spacing:1px">2.1.<span class="l6">4.<span class="w" style="width:31px"></span>Một số h<span class="l7">àm băm t<span class="l7">hông d<span class="l7">ụng</span></span></span></span></span></div>
<div class="ff7" style="font-size:93px">
<span class="a" style="left:760px;top:2031px">2.1.4.1.</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:1158px;top:2017px;word-spacing:3px;letter-spacing:-1px">Thuật toán hàm băm MD5</span></div>
<div class="ff7" style="font-size:93px">
<span class="a" style="left:893px;top:2230px">a.</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:1025px;top:2216px;word-spacing:-2px">Thuật toán hàm băm MD5</span></div>
<div class="ff7" style="font-size:93px">
<span class="a" style="left:959px;top:2429px">-</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:1092px;top:2415px;word-spacing:2px">MD5 (Message-Digest algorithm 5)</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:2569px;top:2416px;word-spacing:1px;letter-spacing:1px">là một hàm băm mật mã được sử dụng</span><span class="a" style="left:1068px;top:2561px">&nbsp;phổ biến, được thiết kể bởi Giáo sư Ronald L. Rivest tại trường MIT vào năm</span><span class="a" style="left:1092px;top:2704px;word-spacing:7px;letter-spacing:3px">1991 để thay thế cho hàm băm trước đó là MD4 (1990). Là một chuẩn</span><span class="a" style="left:1092px;top:2847px;word-spacing:3px;letter-spacing:1px">Internet (RFC 1321), MD5 đã được dùng trong nhiều ứng dụng bảo mật và</span><span class="a" style="left:1092px;top:2990px;word-spacing:1px">cũng được dùng phổ biến để kiểm tra tính toàn vẹn của tập tin. Cũng như các</span><span class="a" style="left:1092px;top:3133px;word-spacing:4px;letter-spacing:1px">hàm băm khác như MD4 và SHS (Secure Hash Standard), MD5 là phương</span><span class="a" style="left:1068px;top:3276px;word-spacing:4px">&nbsp;pháp có ưu điểm tốc độ xử lý rất nhanh, thích hợp với các thông điệp dài và</span><span class="a" style="left:1092px;top:3419px;word-spacing:-2px">cho ra giá trị băm dài <span class="w6"></span>128 bit.</span></div>
<div class="ff7" style="font-size:93px">
<span class="a" style="left:959px;top:3619px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1092px;top:3606px;word-spacing:-1px">Trong MD5, thông điệp ban đầu X sẽ <span class="w6"></span>được mở rộng thành dãy bit X có độ <span class="w6"></span>dài</span><span class="a" style="left:1092px;top:3751px;letter-spacing:1px">là bội của 512. Dãy bit X gồm các thành phần được sắp thứ tự như sau: Dãy</span><span class="a" style="left:1068px;top:3894px;word-spacing:3px">&nbsp;bit X ban đầu, một bit 1, dãy d bit 0 (d được tính sao cho dãy X cuối cùng là</span><span class="a" style="left:1068px;top:4037px;word-spacing:4px;letter-spacing:1px">&nbsp;bội của 512), dãy 64 bit l biểu diễn chiều dài của thông điệp. Đơn vị xử lý</span><span class="a" style="left:1092px;top:4180px;word-spacing:2px">trong MD5 là các từ 32-bit, nên dãy bit X ở trên sẽ được biểu diễn thành dãy</span><span class="a" style="left:1092px;top:4323px;word-spacing:-1px">các từ X[i] 32-bit sau:</span><span class="a" style="left:1350px;top:4510px">X=X[0] X[1] X[2] …X[</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:2285px;top:4509px">N</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:2355px;top:4510px;word-spacing:-1px">−1] , với</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:2709px;top:4509px">N</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:2803px;top:4510px;word-spacing:-2px">là bội của 16.[5]</span></div>
<div class="ff7" style="font-size:93px">
<span class="a" style="left:893px;top:4720px">b.</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:1025px;top:4705px;word-spacing:-2px">Phương pháp MD5 có những ưu điểm sau so với phương pháp MD4</span></div>
<div class="ff7" style="font-size:100px">
<span class="a" style="left:959px;top:4919px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1092px;top:4911px;word-spacing:2px">Thay vì có 3 chu kỳ biến đổi như trong MD4, MD5 bổ sung thêm chu kỳ thứ</span><span class="a" style="left:1092px;top:5058px;word-spacing:-1px">4 để tăng mức độ an toàn.</span><span class="a" style="left:627px;top:5247px">&nbsp;</span></div>
<div class="ff21" style="font-size:99px">
<span class="a" style="left:2241px;top:5253px">12</span></div>
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&nbsp;
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<span class="a" style="left:959px;top:539px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1092px;top:532px">Trong mỗi thao tác của từng chu kỳ, MD5 sử dụng hằng số</span></div>
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<span class="a" style="left:3402px;top:530px">ti</span></div>
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<span class="a" style="left:3462px;top:532px">&nbsp;phân biệt, trong</span><span class="a" style="left:1092px;top:678px;word-spacing:-1px">khi MD4 sử dụng hằng số chung cho mọi thao tác trong cùng chu kỳ biến đổi.</span></div>
<div class="ff7" style="font-size:100px">
<span class="a" style="left:959px;top:889px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1092px;top:881px;word-spacing:1px;letter-spacing:2px">Hàm G ở chu kỳ 2 của MD4: G(X,Y,Z) = ((X</span></div>
<div class="ff4" style="font-size:64px">
<span class="a" style="left:2963px;top:902px">Λ</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:3061px;top:881px">Z)</span></div>
<div class="ff3" style="font-size:57px">
<span class="a" style="left:3198px;top:904px">∨</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:3277px;top:881px">(X</span></div>
<div class="ff4" style="font-size:64px">
<span class="a" style="left:3395px;top:902px">Λ</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:3493px;top:881px">Y)</span></div>
<div class="ff3" style="font-size:57px">
<span class="a" style="left:3641px;top:904px">∨</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:3755px;top:881px">(Y</span></div>
<div class="ff0" style="font-size:83px">
<span class="a" style="left:3942px;top:902px">Z&nbsp;</span></div>
<div class="ff11" style="font-size:63px">
<span class="a" style="left:3871px;top:903px">Λ</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:4028px;top:881px">))</span><span class="a" style="left:1092px;top:1028px;word-spacing:8px;letter-spacing:2px">được thay thế bằng G(X,Y,Z) = (X</span></div>
<div class="ff4" style="font-size:64px">
<span class="a" style="left:2560px;top:1050px">Λ</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:2658px;top:1028px">Z)</span></div>
<div class="ff3" style="font-size:57px">
<span class="a" style="left:2805px;top:1053px">∨</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:2885px;top:1028px">(Y</span></div>
<div class="ff4" style="font-size:64px">
<span class="a" style="left:3002px;top:1050px">Λ</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:3100px;top:1028px">(</span></div>
<div class="ff0" style="font-size:83px">
<span class="a" style="left:3219px;top:1050px">Z&nbsp;</span></div>
<div class="ff11" style="font-size:62px">
<span class="a" style="left:3145px;top:1051px">¬</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:3303px;top:1028px;word-spacing:5px;letter-spacing:3px">)) để giảm tính đối</span><span class="a" style="left:1092px;top:1171px">xứng.</span></div>
<div class="ff7" style="font-size:100px">
<span class="a" style="left:959px;top:1380px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1092px;top:1373px;letter-spacing:1px">Mỗi bước biến đổi trong từng chu kỳ chịu ảnh hưởng kết quả của bước biến</span><span class="a" style="left:1092px;top:1519px;word-spacing:-2px">đổi trước, vì vậy làm tăng nhanh <span class="w6"></span>tốc độ của hiệu ứng <span class="w6"></span>lan truyền (avalanche).</span></div>
<div class="ff7" style="font-size:100px">
<span class="a" style="left:959px;top:1721px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1092px;top:1713px;word-spacing:5px;letter-spacing:1px">Các hệ số dịch chuyển xoay vòng trong mỗi chu kỳ được tối ưu hóa nhằm</span><span class="a" style="left:1092px;top:1860px;word-spacing:2px;letter-spacing:1px">tăng tốc độ hiệu ứng lan truyền. Ngoài ra, mỗi chu kỳ sử dụng 4 hệ số dịch</span><span class="a" style="left:1092px;top:2003px;word-spacing:-2px">chuyển khác nhau.</span></div>
<div class="ff7" style="font-size:100px">
<span class="a" style="left:959px;top:2203px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1092px;top:2196px;word-spacing:3px;letter-spacing:1px">Lý do MD5 được thiết kế thay thế cho MD4 là vì các phân tích chỉ ra rằng</span><span class="a" style="left:1068px;top:2342px;word-spacing:-1px">&nbsp;phương pháp MD4 có vẻ không an toàn. Den Boer và Bosselaers đã chỉ ra các</span><span class="a" style="left:1092px;top:2485px;letter-spacing:1px">điểm yếu trong MD4 trong một bài báo được đăng vào năm 1991và một tấn</span><span class="a" style="left:1092px;top:2628px;word-spacing:-1px">công xung đột đầu tiên được tìm thấy bởi Han Dobbertin vào năm 1996 .</span></div>
<div class="ff7" style="font-size:100px">
<span class="a" style="left:959px;top:2830px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1092px;top:2822px;word-spacing:3px;letter-spacing:1px">Tuy nhiên, các nỗ lực tấn công, phân tích của các nhà nghiên cứu cho thấy</span><span class="a" style="left:1092px;top:2969px;word-spacing:3px">MD5 cũng không còn an toàn và cần được thay thế bằng một thuật toán băm</span><span class="a" style="left:1092px;top:3112px;word-spacing:8px;letter-spacing:2px">khác như các công bố của Den Boer và Bosselaers năm 1993; của Hans</span><span class="a" style="left:1092px;top:3255px;word-spacing:12px;letter-spacing:2px">Dobbertin năm 1996; của nhóm tác giả Xiaoyun Wang, Dengguo Feng,</span><span class="a" style="left:1092px;top:3398px;word-spacing:2px;letter-spacing:1px">Xuejia Lai, và Hongbo ngày 19/8/2004; của Arjen Lenstra, Xiaoyun Wang,</span><span class="a" style="left:1092px;top:3541px;word-spacing:-2px">và Benne de Weger ngày 1/3/2005; và <span class="w6"></span>của Vlastimil Klima, …</span></div>
<div class="ff23" style="font-size:104px">
<span class="a" style="left:760px;top:3739px">2.1.4.2.</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:1423px;top:3735px;word-spacing:-2px">Chuẩn băm an toàn SHS</span></div>
<div class="ff7" style="font-size:100px">
<span class="a" style="left:959px;top:3949px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1092px;top:3942px;word-spacing:2px;letter-spacing:1px">SHS (Secure Hash Standard) là chuẩn gồm tập hợp các thuật toán băm mật</span><span class="a" style="left:1092px;top:4088px;word-spacing:6px;letter-spacing:1px">mã an toàn (Secure Hash Algorithm – SHA) như SHA-1, SHA-224, SHA-</span><span class="a" style="left:1092px;top:4232px;word-spacing:-1px">256, SHA-384, SHA-512 do NIST</span></div>
<div class="ff2" style="font-size:47px">
<span class="a" style="left:2442px;top:4249px">2</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:2530px;top:4232px;word-spacing:-1px">và NSA</span></div>
<div class="ff1" style="font-size:47px">
<span class="a" style="left:2855px;top:4249px">3</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:2942px;top:4232px;word-spacing:-2px">xây dựng.</span></div>
<div class="ff7" style="font-size:100px">
<span class="a" style="left:959px;top:4442px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1092px;top:4435px;word-spacing:1px;letter-spacing:1px">Phương pháp SHA-1 (cũng như SHA-0) được xây dựng trên cùng cơ sở với</span><span class="a" style="left:1068px;top:4581px;word-spacing:1px">&nbsp;phương pháp MD4 và MD5. Tuy nhiên, phương pháp SHA-1 sử dụng trên hệ</span><span class="a" style="left:1092px;top:4725px;word-spacing:3px">thống Big-endian</span></div>
<div class="ff1" style="font-size:47px">
<span class="a" style="left:1785px;top:4742px">5</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1879px;top:4725px;word-spacing:4px">thay vì Little-endian</span></div>
<div class="ff1" style="font-size:48px">
<span class="a" style="left:2696px;top:4742px">6</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:2790px;top:4725px;word-spacing:1px;letter-spacing:1px">như phương pháp MD4 và MD5.</span><span class="a" style="left:1068px;top:4869px;word-spacing:1px">&nbsp;Ngoài ra, hàm băm SHA-1 tạo ra thông điệp rút gọn kết quả có độ dài 160 bit</span><span class="a" style="left:1092px;top:5012px;word-spacing:-1px">nên thường được sử dụng</span><span class="a" style="left:627px;top:5247px">&nbsp;</span></div>
<div class="ff21" style="font-size:99px">
<span class="a" style="left:2241px;top:5253px">13</span></div>
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<div class="text_layer" style="z-index:2"><div class="ie_fix">
&nbsp;
<div class="ff7" style="font-size:100px">
<span class="a" style="left:959px;top:539px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1092px;top:532px;word-spacing:-1px">Phương pháp SHA-1 giống với MD5 <span class="w6"></span>(cải tiến từ MD4) nhưng thông <span class="w6"></span>điệp tóm</span><span class="a" style="left:1092px;top:678px;word-spacing:2px">tắt được tạo ra có độ dài 160 bit. Dưới đây là một số điểm so sánh giữa MD5</span><span class="a" style="left:1092px;top:821px;word-spacing:-2px">và SHA-1:</span></div>
<div class="ff14" style="font-size:59px">
<span class="a" style="left:1158px;top:1045px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1291px;top:1017px;word-spacing:3px;letter-spacing:2px">Giống như MD5, SHA-1 cũng thêm chu kỳ thứ 4 để tăng mức độ an</span><span class="a" style="left:1291px;top:1160px;word-spacing:1px;letter-spacing:1px">toàn cho thuật toán. Tuy nhiên, chu kỳ 4 của SHA-1 sử dụng lại hàm f&nbsp;</span><span class="a" style="left:1291px;top:1303px;word-spacing:-1px">của chu kỳ thứ 2.</span></div>
<div class="ff14" style="font-size:59px">
<span class="a" style="left:1158px;top:1518px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1291px;top:1491px;word-spacing:5px;letter-spacing:1px">Trong SHA-1, 20 bước biến đổi trong cùng một chu kỳ sử dụng cùng</span><span class="a" style="left:1291px;top:1634px;word-spacing:2px">một hàng số K[t] . Trong khi đó, mỗi bước biến đổi trong cùng một chu</span><span class="a" style="left:1291px;top:1776px;word-spacing:-1px">kỳ của MD5 sử dụng các hằng số khác nhau.</span></div>
<div class="ff14" style="font-size:59px">
<span class="a" style="left:1158px;top:1991px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1291px;top:1964px;word-spacing:4px;letter-spacing:1px">So với MD4, hàm G trong MD5 được thay thế thành hàm mới để làm</span><span class="a" style="left:1291px;top:2107px;letter-spacing:1px">giảm tính đối xứng. Trong khi SHA-1, hàm G trong SHA-1 vẫn giữ lại</span><span class="a" style="left:1291px;top:2250px;word-spacing:-1px">hàm G của MD4.</span></div>
<div class="ff14" style="font-size:59px">
<span class="a" style="left:1158px;top:2464px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1291px;top:2437px;word-spacing:9px;letter-spacing:2px">Cả MD5 và SHA-1, mỗi bước biến đổi trong từng chu kỳ chịu ảnh</span><span class="a" style="left:1291px;top:2580px">hưởng kết quả của biến đổi trước, vì vậy làm tăng nhanh tốc độ của hiệu</span><span class="a" style="left:1291px;top:2723px;word-spacing:-2px">ứng lan truyền.</span><span class="a" style="left:1095px;top:4128px">&nbsp;</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:1599px;top:4302px;word-spacing:-2px">Hình 2.1</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1951px;top:4303px">:</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:2001px;top:4302px;word-spacing:-2px">Đặc điểm của các thuật toán băm SHA</span></div>
<div class="ff7" style="font-size:115px">
<span class="a" style="left:627px;top:4712px;letter-spacing:-1px">2.2.</span></div>
<div class="ff16" style="font-size:133px">
<span class="a" style="left:893px;top:4695px;word-spacing:-1px">Mã hóa thông tin</span></div>
<div class="ff21" style="font-size:99px">
<span class="a" style="left:2241px;top:5253px">14</span></div>
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<span class="a" style="left:959px;top:526px;word-spacing:3px">Có rất nhiều thông tin mà chúng ta không muốn người khác biết khi gửi đi như:</span><span class="a" style="left:826px;top:669px">thông tin về Credit-Card, thông tin về kinh doanh của công ty, thông tin về tài khoản</span><span class="a" style="left:826px;top:812px;word-spacing:-1px">cá nhân, thông tin về cá nhân như số chứng minh thư, số thẻ...</span></div>
<div class="ff21" style="font-size:99px">
<span class="a" style="left:826px;top:1006px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:959px;top:999px;word-spacing:1px;letter-spacing:1px">Các thông tin bí mật được cung cấp cho các máy tính quan mạng Internet bằng</span><span class="a" style="left:826px;top:1142px;word-spacing:-3px;letter-spacing:5px">nh<span class="l10">iề<span class="l11">u <span class="l7">ph<span class="l10">ư<span class="l6">ơn<span class="l10">g <span class="l7">th<span class="l10">ứ<span class="l6">c <span class="l7">kh<span class="l11">ác <span class="l" style="margin-left:-13px">nh<span class="l10">au <span class="l12">ví <span class="l" style="margin-left:-13px">dụ <span class="l12">:<span class="w" style="width:245px"></span>Mộ<span class="l10">t cá<span class="l8">ch b<span class="l8">ảo m<span class="l8">ật đ<span class="l7">ơn g<span class="l7">i<span class="l6">ản n<span class="l7">hư<span class="l11">ng m<span class="l7">in<span class="l10">h</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span><span class="a" style="left:802px;top:1285px;word-spacing:1px;letter-spacing:1px">&nbsp;bạch nhất là lưu các thông tin bí mật trên các bộ nhớ có thể xoá được (Removable</span><span class="a" style="left:826px;top:1428px;word-spacing:3px;letter-spacing:1px">Storage) như đĩa mềm. Tuy nhiên dạng bảo mật phổ biến nhất vẫn là dựa vào quá</span><span class="a" style="left:826px;top:1571px;word-spacing:-2px">trình mã hoá dữ liệu <span class="w6"></span>(Encryption).</span></div>
<div class="ff21" style="font-size:99px">
<span class="a" style="left:826px;top:1765px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:959px;top:1758px;word-spacing:-1px">Các hệ thống mã hoá trong máy tính phổ biến nhất thuộc một trong hai loại sau:</span></div>
<div class="ff14" style="font-size:64px">
<span class="a" style="left:893px;top:1969px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1025px;top:1947px;word-spacing:6px">Mã hoá với khoá đối xứng (Symmetric-key Encryption) : Trong phương pháp</span><span class="a" style="left:1025px;top:2090px;word-spacing:1px;letter-spacing:1px">mã hoá với khoá đối xứng, mỗi máy tính có một khoá bí mật (dạng mã) dùng</span><span class="a" style="left:1025px;top:2233px;word-spacing:3px;letter-spacing:1px">để mã hoá các gói thông tin trước khi chúng được gửi qua mạng tới các máy</span><span class="a" style="left:1025px;top:2376px;word-spacing:3px">tính khác. Phương pháp mã hoá với khoá đối xứng đòi hỏi người sử dụng phải</span><span class="a" style="left:1025px;top:2519px;word-spacing:2px">xác định được những máy tính nào đang liên lạc trao đổi thông tin với nhau để</span><span class="a" style="left:1025px;top:2662px;word-spacing:-2px">cài đặt khoá này trên mỗi <span class="w6"></span>máy.</span></div>
<div class="ff14" style="font-size:64px">
<span class="a" style="left:893px;top:2872px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1025px;top:2850px;word-spacing:-2px">Mã hoá với khoá công <span class="w6"></span>khai (Public-key Encryption).[6]</span></div>
<div class="ff16" style="font-size:133px">
<span class="a" style="left:694px;top:3045px;word-spacing:-1px;letter-spacing:2px">2.3<span class="l6">.<span class="w" style="width:21px"></span>Chữ <span class="l8">ký s<span class="l7">ố</span></span></span></span></div>
<div class="ff7" style="font-size:100px">
<span class="a" style="left:694px;top:3290px">2.3.1.</span></div>
<div class="ff16" style="font-size:117px">
<span class="a" style="left:1158px;top:3275px;word-spacing:2px;letter-spacing:-1px">Chữ ký số</span></div>
<div class="ff21" style="font-size:99px">
<span class="a" style="left:826px;top:3492px">-</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:959px;top:3484px;word-spacing:4px">Chữ ký số (Digital Signature)</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:2222px;top:3485px;word-spacing:2px;letter-spacing:1px">chỉ là tập con của chữ ký điện tử. Chữ ký số là</span><span class="a" style="left:959px;top:3628px">chữ ký điện tử dựa trên kỹ thuật mã hóa với khóa công khai, trong đó, mỗi người</span><span class="a" style="left:959px;top:3771px;word-spacing:1px;letter-spacing:1px">có một cặp khóa (một khóa bí mật và một khóa công khai). Khóa bí mật không</span><span class="a" style="left:935px;top:3914px;word-spacing:2px">&nbsp;bao giờ được công bố, trong khi đó, khóa công khai được tự do sử dụng. Để trao</span><span class="a" style="left:959px;top:4057px;word-spacing:4px">đổi thông điệp bí mật, người gửi sử dụng khóa công khai của người nhận để mã</span><span class="a" style="left:959px;top:4200px;word-spacing:3px;letter-spacing:1px">hóa thông điệp gửi, sau đó, người nhận sẽ sử dụng khóa bí mật tương ứng của</span><span class="a" style="left:959px;top:4343px;word-spacing:-2px">mình để giải mã thông điệp.</span></div>
<div class="ff21" style="font-size:99px">
<span class="a" style="left:826px;top:4537px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:959px;top:4530px;word-spacing:1px;letter-spacing:1px">Chữ ký điện tử là thông tin được mã hoá bằng Khoá riêng của người gửi, được</span><span class="a" style="left:959px;top:4673px;letter-spacing:1px">gửi kèm theo văn bản nhằm đảm bảo cho người nhận định danh, xác thực đúng</span><span class="a" style="left:959px;top:4816px;letter-spacing:1px">nguồn gốc và tính toàn vẹn của tài liệu nhận được. Chữ ký điện tử thể hiện văn</span><span class="a" style="left:935px;top:4959px;word-spacing:-1px;letter-spacing:1px">&nbsp;bản gửi đi là <span class="w7"></span>đã được ký bởi <span class="w6"></span>chính người sở hữu một Khoá riêng tương ứng với</span><span class="a" style="left:959px;top:5102px;word-spacing:-1px">một Chứng chỉ điện tử nào đó.”</span><span class="a" style="left:627px;top:5247px">&nbsp;</span></div>
<div class="ff21" style="font-size:99px">
<span class="a" style="left:2241px;top:5253px">15</span></div>
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&nbsp;
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<span class="a" style="left:826px;top:533px">-</span></div>
<div class="ff8" style="font-size:106px">
<span class="a" style="left:959px;top:527px;word-spacing:3px">Chữ ký số khóa công khai</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:2002px;top:526px">(hay</span><span class="a" style="left:2176px;top:526px"><a rel="nofollow" href="http://vi.wikipedia.org/wiki/H%E1%BA%A1_t%E1%BA%A7ng_kh%C3%B3a_c%C3%B4ng_khai" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvd2lraS9IJUUxJUJBJUExX3QlRTElQkElQTduZ19raCVDMyVCM2FfYyVDMyVCNG5nX2toYWk=">&nbsp;</a></span></div>
<div class="ff8" style="font-size:106px">
<span class="a" style="left:2201px;top:527px;word-spacing:3px"><a rel="nofollow" href="http://vi.wikipedia.org/wiki/H%E1%BA%A1_t%E1%BA%A7ng_kh%C3%B3a_c%C3%B4ng_khai" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvd2lraS9IJUUxJUJBJUExX3QlRTElQkElQTduZ19raCVDMyVCM2FfYyVDMyVCNG5nX2toYWk=">hạ tầng khóa công khai</a></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:3118px;top:526px;letter-spacing:1px">) là mô hình sử dụng các</span><span class="a" style="left:959px;top:669px;word-spacing:3px">kỹ thuật mật mã để gắn với mỗi người sử dụng một cặp khóa công khai - bí mật</span><span class="a" style="left:959px;top:812px;word-spacing:3px;letter-spacing:2px">và qua đó có thể ký các văn bản</span><span class="a" style="left:2310px;top:812px;word-spacing:4px;letter-spacing:1px"><a rel="nofollow" href="http://vi.wikipedia.org/wiki/%C4%90i%E1%BB%87n_t%E1%BB%AD" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvd2lraS8lQzQlOTBpJUUxJUJCJTg3bl90JUUxJUJCJUFE">điện tử</a></span><span class="a" style="left:2624px;top:812px;word-spacing:5px;letter-spacing:1px">cũng như trao đổi các thông tin mật.</span><span class="a" style="left:959px;top:955px;word-spacing:2px;letter-spacing:1px">Khóa công khai thường được phân phối thông qua</span><span class="a" style="left:2993px;top:955px;word-spacing:1px;letter-spacing:1px"><a rel="nofollow" href="http://vi.wikipedia.org/wiki/Ch%E1%BB%A9ng_th%E1%BB%B1c_kh%C3%B3a_c%C3%B4ng_khai" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvd2lraS9DaCVFMSVCQiVBOW5nX3RoJUUxJUJCJUIxY19raCVDMyVCM2FfYyVDMyVCNG5nX2toYWk=">chứng thực khóa công khai</a></span><span class="a" style="left:4069px;top:955px">.</span><span class="a" style="left:959px;top:1098px">Quá trình sử dụng chữ ký số bao gồm 2 quá trình: tạo chữ ký và kiểm tra chữ ký.</span><span class="a" style="left:959px;top:1241px">[7]</span></div>
<div class="ff16" style="font-size:117px">
<span class="a" style="left:627px;top:1435px;word-spacing:-5px;letter-spacing:4px">2.<span class="l8">3.<span class="l9">2.<span class="w" style="width:91px"></span>Tạ<span class="l9">o v<span class="l8">à k<span class="l8">iể<span class="l9">m t<span class="l8">ra <span class="l8">ch<span class="l8">ữ k<span class="l8">ý s<span class="l8">ố</span></span></span></span></span></span></span></span></span></span></span></span></div>
<div class="ff7" style="font-size:93px">
<span class="a" style="left:760px;top:1657px">2.3.2.1.</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:1158px;top:1642px;word-spacing:3px;letter-spacing:-1px">Các thuật toán chữ ký số thông dụng</span></div>
<div class="ff7" style="font-size:79px">
<span class="a" style="left:959px;top:1867px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1092px;top:1843px;word-spacing:2px">Chữ ký số giúp xác định được người tạo ra hay chịu trách nhiệm đối với một</span><span class="a" style="left:1092px;top:1986px">thông điệp được ký. Một phương pháp chữ ký số phải bao gồm ít nhất 3 thuật</span><span class="g" style="top:2129px"><span class="a" style="left:1092px;word-spacing:2px">toán chính, đó là thuật toán dùng để</span></span>
</div>
<div class="ff17" style="font-size:107px">
<span class="a" style="left:2519px;top:2129px;word-spacing:1px">tạo khóa</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:2866px;top:2129px;word-spacing:2px">, thuật toán dùng để</span></div>
<div class="ff17" style="font-size:107px">
<span class="a" style="left:3667px;top:2129px;word-spacing:2px">tạo ra chữ&nbsp;</span><span class="g" style="top:2272px"><span class="a" style="left:1092px;word-spacing:2px;letter-spacing:-1px">ký số&nbsp;</span></span>
</div>
<div class="ff8" style="font-size:106px">
<span class="g" style="top:2272px"><span class="a" style="left:1291px">&nbsp;</span></span>
</div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1315px;top:2272px;word-spacing:-1px">và thuật toán tương ứng để</span></div>
<div class="ff17" style="font-size:107px">
<span class="a" style="left:2345px;top:2272px;word-spacing:-2px">&nbsp;xác nhận chữ ký số&nbsp;</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:3140px;top:2272px">.</span></div>
<div class="ff16" style="font-size:100px">
<span class="a" style="left:760px;top:2420px">2.3.2.2.</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:1092px;top:2413px;word-spacing:3px;letter-spacing:-1px">Thuật toán chữ ký số RSA</span></div>
<div class="ff7" style="font-size:86px">
<span class="a" style="left:495px;top:2587px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1092px;top:2569px;word-spacing:1px">Phương pháp chữ ký số RSA được xây dựng dựa trên thuật toán mã hóa khóa</span><span class="a" style="left:627px;top:2712px;word-spacing:-1px">công khai RSA. Để tạo một cặp khóa, RSA thực hiện các bước sau:</span></div>
<div class="ff14" style="font-size:64px">
<span class="a" style="left:495px;top:2923px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1357px;top:2901px;word-spacing:2px;letter-spacing:1px">Chọn 2 số nguyên tố lớn ngẫu nhiên p, q. Nhằm có sự an toàn tối đa</span><span class="a" style="left:627px;top:3044px;word-spacing:-1px">nên chọn p và q có độ dài bằng nhau.</span></div>
<div class="ff14" style="font-size:64px">
<span class="a" style="left:495px;top:3255px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1357px;top:3233px;word-spacing:-1px">Tính n=pq và φ=(p−1)(q−1).</span></div>
<div class="ff14" style="font-size:64px">
<span class="a" style="left:495px;top:3443px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1357px;top:3421px;word-spacing:6px;letter-spacing:1px">Chọn ngẫu nhiên một số nguyên e (1&lt;e&lt;φ) sao cho gcd(e, φ)=1 với</span><span class="a" style="left:627px;top:3564px;word-spacing:-1px">gcd là ước số chung lớn nhất.</span></div>
<div class="ff14" style="font-size:64px">
<span class="a" style="left:495px;top:3775px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1357px;top:3753px;word-spacing:-1px">Tính: d=e−1 mod φ.</span></div>
<div class="ff7" style="font-size:86px">
<span class="a" style="left:1092px;top:3915px">-</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:1158px;top:3895px;word-spacing:-1px">Kết quả là ta có được cặp khóa</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:2429px;top:3897px;word-spacing:-1px">: khóa công khai (n,e) và khóa bí mật (n,d).</span><span class="a" style="left:1092px;top:4040px;word-spacing:12px">Hai <span class="l9">người <span class="l8">sẽ <span class="l7">sử <span class="l7">dụng <span class="l8">chung <span class="l8">một <span class="l8">hàm <span class="l9">băm <span class="w" style="width:113px"></span>an <span class="l8">toàn <span class="l8">trước <span class="l9">hiện <span class="l8">tượng <span class="l8">xung</span></span></span></span></span></span></span></span></span></span></span></span></span></span></div>
<div class="ff19" style="font-size:71px">
<span class="a" style="left:2787px;top:4057px">ℋ&nbsp;&nbsp;</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:4092px;top:4040px">&nbsp;</span><span class="a" style="left:1092px;top:4183px;word-spacing:-1px">đột. Để ký một thông điệp m, người ký thực hiện các bước sau:</span></div>
<div class="ff14" style="font-size:64px">
<span class="a" style="left:1224px;top:4349px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1357px;top:4327px;word-spacing:15px">Dùng <span class="l" style="margin-left:-16px">hàm <span class="l" style="margin-left:-16px">băm <span class="w" style="width:101px"></span>để <span class="l" style="margin-left:-16px">băm <span class="l" style="margin-left:-16px">thông <span class="l" style="margin-left:-16px">điệp <span class="l" style="margin-left:-16px">m:</span></span></span></span></span></span></span></div>
<div class="ff19" style="font-size:71px">
<span class="a" style="left:1972px;top:4344px">ℋ&nbsp;&nbsp;</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:2947px;top:4326px;letter-spacing:18px">h<span class="l" style="margin-left:-19px">=<span class="w" style="width:74px"></span>(<span class="l" style="margin-left:-18px">m<span class="l" style="margin-left:-20px">)<span class="l" style="margin-left:-18px">.</span></span></span></span></span></div>
<div class="ff25" style="font-size:73px">
<span class="a" style="left:3055px;top:4344px">ℋ&nbsp;</span></div>
<div class="ff14" style="font-size:64px">
<span class="a" style="left:1224px;top:4637px"></span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:1357px;top:4614px;word-spacing:-2px">Tạo chữ ký số</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1952px;top:4615px;word-spacing:-1px">sử dụng khóa bí mật (n,d) để tính:</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:1423px;top:4757px">s=h</span></div>
<div class="ff6" style="font-size:48px">
<span class="a" style="left:1589px;top:4775px">d&nbsp;</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:1681px;top:4757px;word-spacing:2px;letter-spacing:-1px">mod n.</span></div>
<div class="ff7" style="font-size:86px">
<span class="a" style="left:959px;top:4888px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1092px;top:4869px;word-spacing:-1px">Chữ ký của</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:1557px;top:4868px">m</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1661px;top:4869px">là</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:1756px;top:4868px">s</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1817px;top:4869px;word-spacing:-1px">và được gửi kèm với thông điệp m đến người nhận.</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:3818px;top:4868px;word-spacing:-1px">Để xác</span><span class="a" style="left:1092px;top:5011px;word-spacing:-2px">nhận chữ ký, người nhận thực hiện các bước sau:</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:3110px;top:5012px">&nbsp;</span></div>
<div class="ff21" style="font-size:99px">
<span class="a" style="left:2241px;top:5253px">16</span></div>
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&nbsp;
<div class="ff14" style="font-size:64px">
<span class="a" style="left:1224px;top:549px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1357px;top:527px;word-spacing:-1px">Sử dụng khóa công khai (n,e) của người ký để giải mã chữ ký:</span><span class="a" style="left:1490px;top:638px">h=s</span></div>
<div class="ff6" style="font-size:49px">
<span class="a" style="left:1649px;top:653px">e</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1710px;top:638px;word-spacing:-1px">mod n.</span></div>
<div class="ff14" style="font-size:64px">
<span class="a" style="left:1224px;top:772px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1357px;top:750px;word-spacing:15px;letter-spacing:3px">Sử <span class="l7">dụ<span class="l6">ng c<span class="l9">ùn<span class="l7">g h<span class="l6">àm <span class="l6">bă<span class="l6">m <span class="w" style="width:132px"></span>vớ<span class="l7">i n<span class="l6">gư<span class="l7">ời <span class="l6">ký <span class="l6">để <span class="l6">bă<span class="l7">m t<span class="l6">hô<span class="l6">ng <span class="l6">đi<span class="l7">ệp <span class="l6">m: <span class="l7">h</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></div>
<div class="ff19" style="font-size:71px">
<span class="a" style="left:2381px;top:767px">ℋ&nbsp;&nbsp;</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1357px;top:860px">′=H(m).</span></div>
<div class="ff14" style="font-size:64px">
<span class="a" style="left:1224px;top:994px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1357px;top:972px;word-spacing:-1px">Chấp nhận chữ ký nếu h′=h. Ngược lại từ chối chữ ký.</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:296px;top:1080px;word-spacing:-18px;letter-spacing:19px">2<span class="l" style="margin-left:-20px">.<span class="l" style="margin-left:-19px">3<span class="l" style="margin-left:-19px">.<span class="l" style="margin-left:-19px">2<span class="l" style="margin-left:-19px">.<span class="l" style="margin-left:-19px">3<span class="l" style="margin-left:-19px">.<span class="w" style="width:490px"></span>T<span class="l" style="margin-left:-19px">h<span class="l" style="margin-left:-20px">u<span class="l" style="margin-left:-20px">ậ<span class="l" style="margin-left:-19px">t <span class="l" style="margin-left:-20px">t<span class="l" style="margin-left:-20px">o<span class="l" style="margin-left:-19px">á<span class="l" style="margin-left:-19px">n <span class="l" style="margin-left:-20px">c<span class="l" style="margin-left:-20px">h<span class="l" style="margin-left:-20px">ữ <span class="l" style="margin-left:-20px">k<span class="l" style="margin-left:-20px">ý <span class="l" style="margin-left:-19px">s<span class="l" style="margin-left:-21px">ố <span class="l" style="margin-left:-19px">D<span class="l" style="margin-left:-20px">S<span class="l" style="margin-left:-20px">A</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></div>
<div class="ff7" style="font-size:86px">
<span class="a" style="left:959px;top:1211px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1092px;top:1192px;word-spacing:4px;letter-spacing:1px">Thuật toán chữ ký số DSA (Digital Signature Algorithm) được đề nghị bởi</span><span class="a" style="left:1068px;top:1335px;word-spacing:8px;letter-spacing:2px">&nbsp;NIST vào tháng 8/1991 để sử dụng trong chuẩn chữ ký số DSS (Digital</span><span class="a" style="left:1092px;top:1478px;word-spacing:3px">Signature Standard), được chỉ ra trong FIPS 186, được chấp nhận năm 1993.</span><span class="a" style="left:1092px;top:1621px;letter-spacing:1px">Một sửa đổi nhỏ được đưa ra ngày năm 1996 trong FIPS 186-1, chuẩn được</span><span class="a" style="left:1092px;top:1764px;letter-spacing:1px">mở rộng hơn năm 2000, được xem như xem như FIPS 186-2. Việc tạo khóa</span><span class="a" style="left:1092px;top:1907px;word-spacing:5px;letter-spacing:1px">gồm hai bước. Bước thứ nhất là lựa chọn các tham số cho thuật toán được</span><span class="a" style="left:1092px;top:2050px;word-spacing:-1px">chia sẻ giữa các người sử dụng khác nhau trong cùng hệ thống:</span></div>
<div class="ff14" style="font-size:64px">
<span class="a" style="left:1224px;top:2261px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1357px;top:2239px;word-spacing:19px;letter-spacing:1px">Chọn <span class="l" style="margin-left:-17px">một <span class="l" style="margin-left:-17px">hàm <span class="l" style="margin-left:-17px">băm <span class="l" style="margin-left:-17px">mã <span class="l" style="margin-left:-16px">hóa <span class="w" style="width:77px"></span>. <span class="l" style="margin-left:-13px">Tron<span class="l6">g <span class="l" style="margin-left:-13px">DSS <span class="l" style="margin-left:-17px">chuẩ<span class="l6">n <span class="w" style="width:111px"></span>luôn <span class="l" style="margin-left:-17px">là <span class="l" style="margin-left:-16px">SHA-1<span class="l6">,</span></span></span></span></span></span></span></span></span></span></span></span></span></span></div>
<div class="ff19" style="font-size:71px">
<span class="a" style="left:2487px;top:2256px">ℋ <span class="w" style="width:773px"></span>ℋ&nbsp;&nbsp;</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:4092px;top:2239px">&nbsp;</span><span class="a" style="left:1357px;top:2381px;word-spacing:8px;letter-spacing:2px">nhưng các hàm băm tốt hơn trong nhóm SHA cũng đang được sử</span><span class="a" style="left:1357px;top:2524px;word-spacing:2px">dụng. Đôi khi đầu ra của một thuật toán băm mới hơn bị rút ngắn kích</span><span class="a" style="left:1357px;top:2667px;word-spacing:6px;letter-spacing:1px">thước so với các thuật toán băm mới cũ để tương tích với cặp khóa</span><span class="a" style="left:1357px;top:2810px;word-spacing:-3px">hiện có.</span></div>
<div class="ff14" style="font-size:64px">
<span class="a" style="left:1224px;top:3021px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1357px;top:2999px;letter-spacing:1px">Chọn kích thước khóa L. Đây là thước đo chính quyết định sức mạnh</span><span class="a" style="left:1357px;top:3142px;word-spacing:10px;letter-spacing:4px">mã hóa của khóa. DSS chuẩn ràng buộc L là bội số của 64 và</span><span class="a" style="left:1357px;top:3285px;word-spacing:3px">512≤L≤1024. Sau đó, FIPS 186-2 xác định L luôn là 1024. Không lâu</span><span class="a" style="left:1357px;top:3428px;word-spacing:-1px">sau, NIST 800-57 đề nghị độ dài khóa là 2048 (hoặc 3072) để thời gian</span><span class="a" style="left:1357px;top:3571px;letter-spacing:1px">an toàn đến năm 2010 (hoặc 2030), sử dụng tương ứng với các giá trị</span><span class="a" style="left:1333px;top:3714px;word-spacing:4px;letter-spacing:1px">&nbsp;băm và q dài hơn. Bản thảo FIPS 186-3 cũng tính đến các hàm băm</span><span class="a" style="left:1357px;top:3857px;word-spacing:-2px">sau này và các khóa <span class="w6"></span>dài hơn.</span></div>
<div class="ff14" style="font-size:64px">
<span class="a" style="left:1224px;top:4067px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1357px;top:4045px;word-spacing:6px">Chọn <span class="l7">một <span class="l7">số ng<span class="l6">uyên <span class="l7">tố <span class="l6">q <span class="l6">cùng <span class="l7">số <span class="l6">bit <span class="l7">với <span class="l7">đầu <span class="l7">ra <span class="l6">của <span class="w" style="width:85px"></span>.</span></span></span></span></span></span></span></span></span></span></span></span></span></div>
<div class="ff19" style="font-size:71px">
<span class="a" style="left:3358px;top:4063px">ℋ&nbsp;&nbsp;</span></div>
<div class="ff14" style="font-size:64px">
<span class="a" style="left:1224px;top:4257px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1357px;top:4235px;word-spacing:2px">Chọn một số nguyên tố p độ dài L bit sao cho p–1 là bội của q. Tức là</span><span class="a" style="left:1333px;top:4378px;word-spacing:-1px">&nbsp;p=qz–1 với số nguyên z nào đó.</span></div>
<div class="ff14" style="font-size:64px">
<span class="a" style="left:1224px;top:4544px"></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1357px;top:4522px;word-spacing:1px;letter-spacing:1px">Chọn g = h</span></div>
<div class="ff22" style="font-size:48px">
<span class="a" style="left:2021px;top:4538px">q</span><span class="a" style="left:1845px;top:4538px">&nbsp;p</span></div>
<div class="ff2" style="font-size:46px">
<span class="g" style="top:4540px"><span class="a" style="left:1991px">/</span><span class="a" style="left:1959px">)</span><span class="a" style="left:1926px">1</span><span class="a" style="left:1818px">(</span></span>
</div>
<div class="ff20" style="font-size:72px">
<span class="a" style="left:1893px;top:4503px">−</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:2106px;top:4522px;letter-spacing:1px">mod p với h bất kỳ (1&lt;h&lt;p–1), và chọn lại nếu kết</span><span class="a" style="left:1357px;top:4634px;letter-spacing:1px">quả là 1. Hầu hết cách chọn h đều nhận được g có thể sử dụng, thông</span><span class="a" style="left:1357px;top:4743px;word-spacing:-1px">thường chọn h=2.</span><span class="a" style="left:627px;top:5247px">&nbsp;</span></div>
<div class="ff21" style="font-size:99px">
<span class="a" style="left:2241px;top:5253px">17</span></div>
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&nbsp;
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1092px;top:526px;letter-spacing:1px">Việc kiểm tra tại server hoàn tất, 1 bản chứng thực số được tạo ra và lưu tại</span><span class="a" style="left:1092px;top:669px">server&nbsp;</span></div>
<div class="ff16" style="font-size:117px">
<span class="a" style="left:627px;top:2432px;word-spacing:-11px;letter-spacing:7px">3<span class="l7">.<span class="l7">3<span class="l8">.<span class="l7">2<span class="l7">.<span class="w" style="width:92px"></span>C<span class="l8">h<span class="l7">ứ<span class="l7">n<span class="l8">g t<span class="l11">h<span class="l8">ự<span class="l7">c</span></span></span></span></span></span></span></span></span></span></span></span></span></div>
<div class="ff7" style="font-size:115px">
<span class="a" style="left:826px;top:2656px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:959px;top:2660px;word-spacing:-1px">Bên cạnh việc cấp phát 1 PKI cơ bản còn có vai trò xác thực 1 chứng thực số.</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:1794px;top:5024px;word-spacing:3px;letter-spacing:-1px">Hình 3.9 : Xác thực chứng thực số</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:627px;top:5247px">&nbsp;</span></div>
<div class="ff21" style="font-size:99px">
<span class="a" style="left:2241px;top:5253px">42</span></div>
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<div class="ff7" style="font-size:79px">
<span class="a" style="left:826px;top:746px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:959px;top:722px">Một client khác hoặc một người thứ 3 có thể gửi ID chứng thực số của một client</span><span class="a" style="left:959px;top:865px;word-spacing:11px;letter-spacing:4px">để biết được client đó có tồn tại hay không. Bằng cách kích vào Menu</span><span class="a" style="left:959px;top:1008px;word-spacing:9px">CheckUser. <span class="w" style="width:25px"></span>Thông tin <span class="l8">server <span class="w" style="width:26px"></span>trả về <span class="l8">có thể <span class="l8">là Ok(nếu <span class="l7">tồn tại <span class="l9">client), fa<span class="l6">iled user&nbsp;</span></span></span></span></span></span></span><span class="a" style="left:959px;top:1151px;word-spacing:-2px">was expired(nếu client đó đã hết hạn), <span class="w6"></span>failed(nếu không tồn tại user đó.</span></div>
<div class="ff16" style="font-size:117px">
<span class="a" style="left:694px;top:1345px;word-spacing:-6px;letter-spacing:2px">3.3<span class="l7">.3.<span class="w" style="width:26px"></span>Toà<span class="l7">n vẹn dữ l<span class="l6">iệu</span></span></span></span></div>
<div class="ff7" style="font-size:79px">
<span class="a" style="left:826px;top:1578px">-</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:959px;top:1554px;word-spacing:-1px">Client gửi tin nhắn đến server để đăng ký chứng thực số. <span class="w7"></span>Nếu tin nhắn bị thay đổi</span><span class="a" style="left:959px;top:1697px;word-spacing:-1px">đồng nghĩa với việc gia trị băm(H(m)) cũng <span class="w7"></span>bị thay đổi. Do vậy trong <span class="w6"></span>trường hợp</span><span class="a" style="left:959px;top:1840px;word-spacing:1px">thẩm tra chữ ký số là đúng đắn tương ứng với giá trị băm H(m) đúng và tin nhắn</span><span class="a" style="left:959px;top:1983px;word-spacing:-1px">gửi đi và tin nhắn nhận được tại server là trùng nhau. Như vậy thông tin mà client</span><span class="a" style="left:959px;top:2126px;word-spacing:4px;letter-spacing:1px">gửi lên server hoàn toàn không bị thay đổi.Ngoài các chức năng trên Platform</span><span class="a" style="left:959px;top:2269px;word-spacing:7px;letter-spacing:1px">PKI còn bao gồm các chức năng như: Kiểm tra những client hết hạn sử dụng</span><span class="a" style="left:959px;top:2412px;word-spacing:-2px">chức thực số, tìm kiếm,xóa, sửa 1 <span class="w7"></span>chứng thực số.</span><span class="a" style="left:627px;top:5247px">&nbsp;</span></div>
<div class="ff21" style="font-size:99px">
<span class="a" style="left:2241px;top:5253px">43</span></div>
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&nbsp;
<div class="ff16" style="font-size:109px">
<span class="a" style="left:1358px;top:2996px;word-spacing:-2px">Hình 3.10 : Form tìm kiếm, sửa, xóa thông tin <span class="w6"></span>chứng thực số</span></div>
<div class="ff7" style="font-size:100px">
<span class="a" style="left:694px;top:3209px">3.3.4.</span></div>
<div class="ff21" style="font-size:115px">
<span class="a" style="left:1158px;top:3194px">&nbsp;</span></div>
<div class="ff16" style="font-size:117px">
<span class="a" style="left:1184px;top:3193px;word-spacing:-2px">Thu hồi và cấp phát lại chứng thực số</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:760px;top:3402px;word-spacing:-1px;letter-spacing:3px">3.<span class="l7">3.4<span class="l9">.1<span class="l6">.<span class="w" style="width:42px"></span>Th<span class="l7">u <span class="l6">hồ<span class="l7">i</span></span></span></span></span></span></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1092px;top:3600px;word-spacing:1px;letter-spacing:2px">-<span class="w" style="width:32px"></span>Mỗi bản chứ<span class="l6">ng thực số sẽ <span class="w6"></span>đượ<span class="l7">c gán thời gian bắt đầu cấp phá<span class="l6">t. Serv<span class="l7">er sẽ</span></span></span></span></span><span class="a" style="left:1092px;top:3743px;word-spacing:4px;letter-spacing:1px">kiểm tra và so sánh khoảng thời gian cấp phát chứng thực số đến thời gian</span><span class="a" style="left:1092px;top:3886px;word-spacing:2px">hiện tại. Nếu thời gian đã hết hạn chứng thực số đó sẽ bị thu hồi và được lưu</span><span class="a" style="left:1092px;top:4029px;word-spacing:-1px">lại vào bảng cơ sở dữ liệu chứa “Chứng thực số hệt quyền hạn sử dụng”</span><span class="a" style="left:627px;top:5247px">&nbsp;</span></div>
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<span class="a" style="left:2241px;top:5253px">44</span></div>
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&nbsp;
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<span class="a" style="left:1212px;top:3994px;word-spacing:-2px">Hình 3.11 : Kiểm tra và <span class="w6"></span>thu hồi chứng thực số hết hạn sử dụng</span></div>
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<span class="a" style="left:627px;top:5247px">&nbsp;</span></div>
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<span class="a" style="left:959px;top:1027px;word-spacing:1px;letter-spacing:2px">3.3<span class="l7">.4.<span class="l6">2.<span class="w" style="width:41px"></span>Cấp <span class="l11">ph<span class="l6">át <span class="l7">lại</span></span></span></span></span></span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:761px;top:1225px;word-spacing:-3px;letter-spacing:10px">-<span class="w" style="width:488px"></span>S<span class="l11">e<span class="l11">r<span class="l10">v<span class="l10">e<span class="l10">r <span class="l6">n<span class="l10">h<span class="l11">ậ<span class="l10">n <span class="l6">t<span class="l11">h<span class="l10">ấ<span class="l10">y <span class="l6">1 <span class="l6">c<span class="l11">h<span class="l10">ứ<span class="l11">n<span class="l10">g t<span class="l" style="margin-left:-16px">h<span class="l10">ứ<span class="l10">c <span class="l6">s<span class="l10">ố <span class="l6">đ<span class="l10">ã <span class="l7">b<span class="l10">ị <span class="l6">l<span class="l10">ộ<span class="l11">, <span class="l6">h<span class="l10">o<span class="l10">ặ<span class="l11">c <span class="l6">c<span class="l11">l<span class="l10">i<span class="l11">e<span class="l10">n<span class="l10">t <span class="l6">c<span class="l11">ả<span class="l10">m <span class="l7">n<span class="l10">h<span class="l11">ậ<span class="l10">n <span class="l6">t<span class="l10">h<span class="l10">ấ<span class="l10">y</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span><span class="a" style="left:893px;top:1367px">khóa bí mật của mình và các thông tin quan trọng khác bị rò rỉ. Client sẽ gửi thông</span><span class="a" style="left:869px;top:1510px;word-spacing:3px">&nbsp;báo đến server và yêu cầu đăng ký 1 bản chứng thực số khác. Về phía server, Khi</span><span class="a" style="left:869px;top:1653px;word-spacing:3px">&nbsp;phát hiện thấy 1 chứng thực số bị lộ hoặc rò rỉ thông tin sẽ gửi yêu cầu đến client</span><span class="a" style="left:893px;top:1796px;word-spacing:-1px">yêu cầu client đăng ký 1 bản chứng thực số khác.</span></div>
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<span class="a" style="left:2241px;top:5253px">47</span></div>
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<span class="a" style="left:2181px;top:1781px;word-spacing:-2px">KẾT LUẬN</span></div>
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<span class="a" style="left:760px;top:2221px;word-spacing:4px;letter-spacing:1px">Đề tài “Hạ tầng khóa công khai (PKI), vấn đề cấp phát chứng thực số và ứng dụng</span><span class="a" style="left:760px;top:2364px;word-spacing:3px">trong thương mại điện tử” là một đề tài khó và rộng. Trong thời gian nghiên cứu, tìm</span><span class="a" style="left:760px;top:2507px;word-spacing:-1px;letter-spacing:1px">hiểu<span class="l6">, xây <span class="w6"></span>dựng ứng dụng đố <span class="w7"></span>án đã hoàn thành được các nhiệm vụ <span class="w6"></span>được đặt ra, cụ thể</span></span><span class="a" style="left:760px;top:2650px">là:</span></div>
<div class="ff7" style="font-size:79px">
<span class="a" style="left:826px;top:2861px">-</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:959px;top:2836px;word-spacing:5px">Về mặt lý thuyết</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1689px;top:2837px;word-spacing:1px;letter-spacing:1px">: Khóa luận trình bày những khái niệm, đặc điểm cơ bản của</span><span class="a" style="left:959px;top:2980px;word-spacing:3px">một hệ thống PKI. Ứng dụng của hạ tầng khóa công khai trong thương mại điện</span><span class="a" style="left:959px;top:3123px;word-spacing:17px;letter-spacing:5px">tự<span class="l11">. <span class="w" style="width:15px"></span>T<span class="l6">ư <span class="w" style="width:15px"></span>tư<span class="l11">ởn<span class="l10">g <span class="w" style="width:14px"></span>củ<span class="l11">a <span class="w" style="width:15px"></span>t<span class="l6">hu<span class="l10">ật <span class="w9"></span>t<span class="l6">oá<span class="l10">n <span class="w" style="width:14px"></span>cấ<span class="l11">p <span class="w" style="width:14px"></span>ph<span class="l10">át <span class="w9"></span>kh<span class="l10">óa<span class="l11">, <span class="w" style="width:15px"></span>si<span class="l10">nh <span class="w9"></span>và <span class="w9"></span>ki<span class="l11">ểm <span class="w9"></span>t<span class="l6">ra <span class="w10"></span>c<span class="l6">hữ <span class="w10"></span>ký</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span><span class="a" style="left:959px;top:3266px;word-spacing:7px;letter-spacing:2px">số(RSA,DSA,...) về ưu nhược điểm của từng thuật toán, định nghĩa về hàm</span><span class="a" style="left:935px;top:3409px;word-spacing:-2px">&nbsp;băm(hàm băm MD5,SHA-1). Cấp phát và <span class="w6"></span>xác thực chứng thực số.</span></div>
<div class="ff7" style="font-size:86px">
<span class="a" style="left:893px;top:3615px">-</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:1025px;top:3595px;word-spacing:4px;letter-spacing:1px">Về mô phỏng và kết quả thử nghiệm</span></div>
<div class="ff21" style="font-size:99px">
<span class="a" style="left:2625px;top:3603px">:</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:2683px;top:3596px;word-spacing:5px;letter-spacing:1px">Đã hoàn thành việc mô phỏng hoạt</span><span class="a" style="left:1025px;top:3739px;word-spacing:-1px">động cơ bản của một hệ thống PKI.</span><span class="a" style="left:760px;top:3926px;word-spacing:3px;letter-spacing:1px">Mặc dù đã hết sức cố gắng nhưng trình độ chuyên môn và thời gian thực hiện khóa</span><span class="a" style="left:760px;top:4069px;word-spacing:1px">luận còn hạn hẹp, cũng như mức độ phức tạp của đề tài, nên kết quả đạt được còn gặp</span><span class="a" style="left:736px;top:4212px;word-spacing:-2px">&nbsp;phải một số khiếm khuyết.</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:760px;top:4585px;word-spacing:3px">Hướng phát triển đề tài</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1749px;top:4586px;word-spacing:4px">: Tiếp tục hoàn thiện các chức năng, nhằm tăng hiệu quả và</span><span class="a" style="left:760px;top:4729px;word-spacing:4px;letter-spacing:1px">độ an toàn. Cải thiện việc gửi dữ liệu từ client và xử lý tại server để thời gian hoạt</span><span class="a" style="left:760px;top:4872px;word-spacing:-1px">động của cả hệ thống là nhanh nhất và hiệu quả của hệ thông là tốt nhất có thể.</span><span class="a" style="left:627px;top:5247px">&nbsp;</span></div>
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<span class="a" style="left:2241px;top:5253px">48</span></div>
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<span class="a" style="left:1461px;top:1979px;word-spacing:-1px">CÁC TÀI LIỆU THAM KHẢO</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:627px;top:2285px;word-spacing:-4px">[1] William Stallings</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1468px;top:2286px">.</span></div>
<div class="ff8" style="font-size:106px">
<span class="a" style="left:1516px;top:2287px;word-spacing:-2px">Cryptography and Network Security : Principles and <span class="w6"></span>Practice,</span><span class="a" style="left:603px;top:2430px;word-spacing:-1px">&nbsp;Fourth Edition</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1199px;top:2429px;word-spacing:-2px">. Prentice Hall, 2005.</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:627px;top:2615px;word-spacing:-3px">TS.Nguyễn Đại Thọ</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1463px;top:2617px;word-spacing:-1px">Bộ môn Mạng &amp; Truyền thông Máy tính Khoa Công nghệ Thông</span><span class="a" style="left:627px;top:2760px;word-spacing:-1px">tin Slide bài giảng AN TOÀN MẠNG - (Chương 3 – <span class="w6"></span>trang 96).</span><span class="a" style="left:627px;top:2947px;color:#0000ff"><a rel="nofollow" href="http://vi.wikipedia.org/wiki/M%E1%BA%ADt_m%C3%A3_h%C3%B3a_kh%C3%B3a_c%C3%B4ng_khai" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvd2lraS9NJUUxJUJBJUFEdF9tJUMzJUEzX2glQzMlQjNhX2toJUMzJUIzYV9jJUMzJUI0bmdfa2hhaQ==">http://vi.wikipedia.org/wiki/M%E1%BA%ADt_m%C3%A3_h%C3%B3a_kh</a></span><span class="a" style="left:627px;top:3090px;color:#0000ff"><a rel="nofollow" href="http://vi.wikipedia.org/wiki/M%E1%BA%ADt_m%C3%A3_h%C3%B3a_kh%C3%B3a_c%C3%B4ng_khai" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvd2lraS9NJUUxJUJBJUFEdF9tJUMzJUEzX2glQzMlQjNhX2toJUMzJUIzYV9jJUMzJUI0bmdfa2hhaQ==">%C3%B3a_c%C3%B4ng_khai</a></span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:627px;top:3275px;word-spacing:-2px">[2], [3] Đinh Mạnh Tường</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1742px;top:3277px;word-spacing:-2px">– Giáo trình “Cấu trúc dữ <span class="w7"></span>liệu và giải thuật”</span><span class="a" style="left:627px;top:3464px;word-spacing:-1px">(Chương 1 trang 12-16).</span></div>
<div class="ff16" style="font-size:100px">
<span class="a" style="left:627px;top:3657px">[4]</span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:753px;top:3650px;word-spacing:-3px">TS.Nguyễn Đại Thọ</span></div>
<div class="ff21" style="font-size:107px">
<span class="a" style="left:1588px;top:3651px;word-spacing:-1px">Bộ môn Mạng &amp; Truyền thông Máy tính Khoa Công nghệ</span><span class="a" style="left:627px;top:3794px;word-spacing:-1px">Thông tin. Slide bài giảng AN TOÀN MẠNG - (Chương 4 – trang 116).</span><span class="a" style="left:627px;top:3981px;color:#0000ff"><a rel="nofollow" href="http://vi.wikipedia.org/wiki/H%C3%A0m_b%C4%83m_m%E1%BA%ADt_m%C3%A3_h%E1%BB%8Dc" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvd2lraS9IJUMzJUEwbV9iJUM0JTgzbV9tJUUxJUJBJUFEdF9tJUMzJUEzX2glRTElQkIlOERj">http://vi.wikipedia.org/wiki/H%C3%A0m_b%C4%83m_m%E1%BA%ADt_m</a></span><span class="a" style="left:627px;top:4124px;color:#0000ff"><a rel="nofollow" href="http://vi.wikipedia.org/wiki/H%C3%A0m_b%C4%83m_m%E1%BA%ADt_m%C3%A3_h%E1%BB%8Dc" target="_blank" class="ll" orig="aHR0cDovL3ZpLndpa2lwZWRpYS5vcmcvd2lraS9IJUMzJUEwbV9iJUM0JTgzbV9tJUUxJUJBJUFEdF9tJUMzJUEzX2glRTElQkIlOERj">%C3%A3_h%E1%BB%8Dc</a></span></div>
<div class="ff16" style="font-size:109px">
<span class="a" style="left:627px;top:4310px">[5],[8]</span><span class="a" style="left:899px;top:4310px;word-spacing:-4px"><a rel="nofollow" href="http://gralib.hcmuns.edu.vn/gsdl/collect/thacsi2/index/assoc/HASH4541.dir/5.pdf" target="_blank" class="ll" orig="aHR0cDovL2dyYWxpYi5oY211bnMuZWR1LnZuL2dzZGwvY29sbGVjdC90aGFjc2kyL2luZGV4L2Fzc29jL0hBU0g0NTQxLmRpci81LnBkZg==">Đặng Bình Phương</a></span></div>
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<span class="a" style="left:627px;top:4827px">[7]</span></div>
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<span class="a" style="left:763px;top:4829px;word-spacing:-1px">Chứng thực điện tử&amp;Chữ ký điện tử(HÀ NỘI –IT Week 2004) – VASC CA</span></div>
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<span class="a" style="left:627px;top:5015px">[9]</span></div>
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<span class="a" style="left:739px;top:5016px">&nbsp;</span></div>
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<span class="a" style="left:763px;top:5015px;word-spacing:-4px">Carlisle Adams, Steve Lloyd</span></div>
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<span class="a" style="left:627px;top:5247px">&nbsp;</span></div>
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<div id="rightcolumn_ad_gam" style="clear: both; margin-bottom: 15px;"><div id="Doc_Sideboard_MediumRectangle_ATF_300x250"></div><script type="text/javascript">Scribd.Ads.addUnit('Doc_Sideboard_MediumRectangle_ATF_300x250');</script><iframe style="border: 0pt none;" marginheight="0" marginwidth="0" name="google_ads_iframe_/1024966/ca-pub-7291399211842501/Doc_Sideboard_MediumRectangle_ATF_300x250_0" id="google_ads_iframe_/1024966/ca-pub-7291399211842501/Doc_Sideboard_MediumRectangle_ATF_300x250_0" frameborder="0" height="250" scrolling="no" width="300"></iframe><iframe style="border: 0pt none; visibility: hidden; display: none;" marginheight="0" marginwidth="0" name="google_ads_iframe_/1024966/ca-pub-7291399211842501/Doc_Sideboard_MediumRectangle_ATF_300x250_0__hidden__" id="google_ads_iframe_/1024966/ca-pub-7291399211842501/Doc_Sideboard_MediumRectangle_ATF_300x250_0__hidden__" frameborder="0" height="0" scrolling="no" width="0"></iframe></div><div class="autogen_class_views_documents_fourgen_toc" id="autogen_id_538590085"><div id="sectionlist"><span class="toc_header"><span class="sections_icon"></span><span class="toc_title"><h3>Sections</h3></span><span class="toc_control"><span class="expand_collapse"><a class="toc_show_all" href="#" onclick="if (!Scribd.TOC) $$('#sectionlist li').each(Element.show);" rel="nofollow">show all</a><a class="toc_collapse" href="#" rel="nofollow" style="display: none;">collapse</a></span><span class="toc_prev_next"><a class="toc_prev grey" href="#" rel="nofollow">« prev</a> | <a class="toc_next " href="#" rel="nofollow">next »</a></span></span></span><ul class="notranslate" data-page-count="5"><li class="toc_section toc_section_1 " data-first-page="9" data-section="1"><a href="http://www.scribd.com/doc/61105136/1/M%E1%BA%ADt-ma-h%E1%BB%8Dc-khoa-cong-khai-Phi-%C4%91%E1%BB%91i-x%E1%BB%A9ng-la-gi" class="toc_section_link" data-first-page="9" data-section="1">1.1.1.1. Mật mã học khóa công khai (Phi đối xứng) là gì</a></li><li class="toc_section toc_section_1 " data-first-page="9" data-section="2"><a href="http://www.scribd.com/doc/61105136/2/M%E1%BB%A5c-%C4%91ich-c%E1%BB%A7a-h%E1%BB%87-th%E1%BB%91ng-ma-hoa-cong-khai" class="toc_section_link" data-first-page="9" data-section="2">1.1.1.2.Mục đích của hệ thống mã hoá công khai :</a></li><li class="toc_section toc_section_1 " data-first-page="11" data-section="3"><a href="http://www.scribd.com/doc/61105136/3/%E1%BB%A8ng-d%E1%BB%A5ng" class="toc_section_link" data-first-page="11" data-section="3">1.1.2.Ứng dụng</a></li><li class="toc_section toc_section_1 " data-first-page="12" data-section="4"><a href="http://www.scribd.com/doc/61105136/4/Thu%E1%BA%ADt-toan" class="toc_section_link" data-first-page="12" data-section="4">1.2.1.Thuật toán</a></li><li class="toc_section toc_section_1 " data-first-page="12" data-section="5"><a href="http://www.scribd.com/doc/61105136/5/Tinh-hi%E1%BB%87u-qu%E1%BA%A3-c%E1%BB%A7a-thu%E1%BA%ADt-toan" class="toc_section_link" data-first-page="12" data-section="5">1.2.2.1.Tính hiệu quả của thuật toán</a></li><li class="toc_section toc_section_1 " data-first-page="12" data-section="6"><a href="http://www.scribd.com/doc/61105136/6/%C4%90anh-gia-th%E1%BB%9Di-gian-th%E1%BB%B1c-hi%E1%BB%87n-thu%E1%BA%ADt-toan" class="toc_section_link" data-first-page="12" data-section="6">1.2.2.2.Đánh giá thời gian thực hiện thuật toán</a></li><li class="toc_section toc_section_1 " data-first-page="13" data-section="7"><a href="http://www.scribd.com/doc/61105136/7/PKI-la-gi" class="toc_section_link" data-first-page="13" data-section="7">1.3.1.PKI là gì</a></li><li class="toc_section toc_section_1 " data-first-page="13" data-section="8"><a href="http://www.scribd.com/doc/61105136/8/C%E1%BB%9F-s%E1%BB%9F-h%E1%BA%A1-t%E1%BA%A7ng-khoa-cong-khai" class="toc_section_link" data-first-page="13" data-section="8">1.3.2.Cở sở hạ tầng khóa công khai</a></li><li class="toc_section toc_section_1 " data-first-page="15" data-section="9"><a href="http://www.scribd.com/doc/61105136/9/M%E1%BB%99t-s%E1%BB%91-%E1%BB%A9ng-d%E1%BB%A5ng" class="toc_section_link" data-first-page="15" data-section="9">1.4.1.Một số ứng dụng</a></li><li style="display: none;" class="toc_section toc_section_2 not_first_page" data-first-page="15" data-section="10"><a href="http://www.scribd.com/doc/61105136/10/M%E1%BB%99t-s%E1%BB%91-h%E1%BB%87-th%E1%BB%91ng-PKI" class="toc_section_link" data-first-page="15" data-section="10">1.4.2.Một số hệ thống PKI</a></li><li style="display: none;" class="toc_section toc_section_2 not_first_page" data-first-page="16" data-section="11"><a href="http://www.scribd.com/doc/61105136/11/M%E1%BB%A5c-%C4%91ich-c%E1%BB%A7a-%C4%91%E1%BB%81-tai" class="toc_section_link" data-first-page="16" data-section="11">1.5.Mục đích của đề tài</a></li><li style="display: none;" class="toc_section toc_section_2 not_first_page" data-first-page="16" data-section="12"><a href="http://www.scribd.com/doc/61105136/12/%C4%90%E1%BA%B7t-v%E1%BA%A7n-%C4%91%E1%BB%81" class="toc_section_link" data-first-page="16" data-section="12">1.6.Đặt vần đề ?</a></li><li style="display: none;" class="toc_section toc_section_2 not_first_page" data-first-page="17" data-section="13"><a href="http://www.scribd.com/doc/61105136/13/Cac-v%E1%BA%A5n-%C4%91%E1%BB%81-s%E1%BA%BD-gi%E1%BA%A3i-quy%E1%BA%BFt-trong-khoa-lu%E1%BA%ADn" class="toc_section_link" data-first-page="17" data-section="13">1.7.Các vấn đề sẽ giải quyết trong khóa luận</a></li><li style="display: none;" class="toc_section toc_section_2 not_first_page" data-first-page="18" data-section="14"><a href="http://www.scribd.com/doc/61105136/14/Ham-b%C4%83m" class="toc_section_link" data-first-page="18" data-section="14">2.1.1.Hàm băm</a></li><li style="display: none;" class="toc_section toc_section_2 not_first_page" data-first-page="18" data-section="15"><a href="http://www.scribd.com/doc/61105136/15/Ham-b%C4%83m-m%E1%BA%ADt-ma-h%E1%BB%8Dc" class="toc_section_link" data-first-page="18" data-section="15">2.1.2.Hàm băm mật mã học</a></li><li style="display: none;" class="toc_section toc_section_2 not_first_page" data-first-page="18" data-section="16"><a href="http://www.scribd.com/doc/61105136/16/%C4%90%E1%BA%A3m-b%E1%BA%A3o-tinh-toan-v%E1%BA%B9n-d%E1%BB%AF-li%E1%BB%87u" class="toc_section_link" data-first-page="18" data-section="16">2.1.3.Đảm bảo tính toàn vẹn dữ liệu</a></li><li style="display: none;" class="toc_section toc_section_2 not_first_page" data-first-page="19" data-section="17"><a href="http://www.scribd.com/doc/61105136/17/Thu%E1%BA%ADt-toan-ham-b%C4%83m-MD5" class="toc_section_link" data-first-page="19" data-section="17">2.1.4.1.Thuật toán hàm băm MD5</a></li><li style="display: none;" class="toc_section toc_section_2 not_first_page" data-first-page="20" data-section="18"><a href="http://www.scribd.com/doc/61105136/18/Chu%E1%BA%A9n-b%C4%83m-an-toan-SHS" class="toc_section_link" data-first-page="20" data-section="18">2.1.4.2. Chuẩn băm an toàn SHS</a></li><li style="display: none;" class="toc_section toc_section_2 not_first_page" data-first-page="21" data-section="19"><a href="http://www.scribd.com/doc/61105136/19/Ma-hoa-thong-tin" class="toc_section_link" data-first-page="21" data-section="19">2.2.Mã hóa thông tin</a></li><li style="display: none;" class="toc_section toc_section_3 not_first_page" data-first-page="22" data-section="20"><a href="http://www.scribd.com/doc/61105136/20/Ch%E1%BB%AF-k%C3%BD-s%E1%BB%91" class="toc_section_link" data-first-page="22" data-section="20">2.3.1.Chữ ký số</a></li><li style="display: none;" class="toc_section toc_section_3 not_first_page" data-first-page="23" data-section="21"><a href="http://www.scribd.com/doc/61105136/21/Cac-thu%E1%BA%ADt-toan-ch%E1%BB%AF-k%C3%BD-s%E1%BB%91-thong-d%E1%BB%A5ng" class="toc_section_link" data-first-page="23" data-section="21">2.3.2.1.Các thuật toán chữ ký số thông dụng</a></li><li style="display: none;" class="toc_section toc_section_3 not_first_page" data-first-page="23" data-section="22"><a href="http://www.scribd.com/doc/61105136/22/Thu%E1%BA%ADt-toan-ch%E1%BB%AF-k%C3%BD-s%E1%BB%91-RSA" class="toc_section_link" data-first-page="23" data-section="22">2.3.2.2.Thuật toán chữ ký số RSA</a></li><li style="display: none;" class="toc_section toc_section_3 not_first_page" data-first-page="24" data-section="23"><a href="http://www.scribd.com/doc/61105136/23/Thu%E1%BA%ADt-toan-ch%E1%BB%AF-k%C3%BD-s%E1%BB%91-DSA" class="toc_section_link" data-first-page="24" data-section="23">2.3.2.3. Thuật toán chữ ký số DSA</a></li><li style="display: none;" class="toc_section toc_section_3 not_first_page" data-first-page="26" data-section="24"><a href="http://www.scribd.com/doc/61105136/24/K%E1%BA%BFt-qu%E1%BA%A3-th%E1%BB%AD-nghi%E1%BB%87m-va-nh%E1%BA%ADn-xet" class="toc_section_link" data-first-page="26" data-section="24">2.3.2.4. Kết quả thử nghiệm và nhận xét</a></li><li style="display: none;" class="toc_section toc_section_3 not_first_page" data-first-page="30" data-section="25"><a href="http://www.scribd.com/doc/61105136/25/Ch%E1%BB%A9ng-th%E1%BB%B1c-s%E1%BB%91" class="toc_section_link" data-first-page="30" data-section="25">2.4.Chứng thực số</a></li><li style="display: none;" class="toc_section toc_section_3 not_first_page" data-first-page="30" data-section="26"><a href="http://www.scribd.com/doc/61105136/26/C%E1%BA%A5u-truc-phan-t%E1%BA%A7ng-c%E1%BB%A7a-h%E1%BB%87-th%E1%BB%91ng-PKI" class="toc_section_link" data-first-page="30" data-section="26">2.5.Cấu trúc phân tầng của hệ thống PKI</a></li><li style="display: none;" class="toc_section toc_section_3 not_first_page" data-first-page="31" data-section="27"><a href="http://www.scribd.com/doc/61105136/27/C%E1%BA%A5p-phat-ch%E1%BB%A9ng-th%E1%BB%B1c-s%E1%BB%91" class="toc_section_link" data-first-page="31" data-section="27">2.6.1.Cấp phát chứng thực số</a></li><li style="display: none;" class="toc_section toc_section_3 not_first_page" data-first-page="32" data-section="28"><a href="http://www.scribd.com/doc/61105136/28/Xac-th%E1%BB%B1c-ch%E1%BB%A9ng-th%E1%BB%B1c-s%E1%BB%91" class="toc_section_link" data-first-page="32" data-section="28">2.6.2.Xác thực chứng thực số</a></li><li style="display: none;" class="toc_section toc_section_3 not_first_page" data-first-page="33" data-section="29"><a href="http://www.scribd.com/doc/61105136/29/Ma-hoa" class="toc_section_link" data-first-page="33" data-section="29">2.7.1.Mã hóa</a></li><li style="display: none;" class="toc_section toc_section_4 not_first_page" data-first-page="33" data-section="30"><a href="http://www.scribd.com/doc/61105136/30/Ch%E1%BB%91ng-gi%E1%BA%A3-m%E1%BA%A1o" class="toc_section_link" data-first-page="33" data-section="30">2.7.2.Chống giả mạo</a></li><li style="display: none;" class="toc_section toc_section_4 not_first_page" data-first-page="34" data-section="31"><a href="http://www.scribd.com/doc/61105136/31/Xac-th%E1%BB%B1c" class="toc_section_link" data-first-page="34" data-section="31">2.7.3.Xác thực</a></li><li style="display: none;" class="toc_section toc_section_4 not_first_page" data-first-page="34" data-section="32"><a href="http://www.scribd.com/doc/61105136/32/Ch%E1%BB%91ng-ch%E1%BB%91i-b%E1%BB%8F-ngu%E1%BB%93n-g%E1%BB%91c" class="toc_section_link" data-first-page="34" data-section="32">2.7.4.Chống chối bỏ nguồn gốc</a></li><li style="display: none;" class="toc_section toc_section_4 not_first_page" data-first-page="34" data-section="33"><a href="http://www.scribd.com/doc/61105136/33/Ch%E1%BB%AF-k%C3%BD-%C4%91i%E1%BB%87n-t%E1%BB%AD" class="toc_section_link" data-first-page="34" data-section="33">2.7.5.Chữ ký điện tử</a></li><li style="display: none;" class="toc_section toc_section_4 not_first_page" data-first-page="35" data-section="34"><a href="http://www.scribd.com/doc/61105136/34/B%E1%BA%A3o-m%E1%BA%ADt-website" class="toc_section_link" data-first-page="35" data-section="34">2.7.6.Bảo mật website</a></li><li style="display: none;" class="toc_section toc_section_4 not_first_page" data-first-page="35" data-section="35"><a href="http://www.scribd.com/doc/61105136/35/%C4%90%E1%BA%A3m-b%E1%BA%A3o-ph%E1%BA%A7n-m%E1%BB%81m" class="toc_section_link" data-first-page="35" data-section="35">2.7.7.Đảm bảo phần mềm</a></li><li style="display: none;" class="toc_section toc_section_4 not_first_page" data-first-page="35" data-section="36"><a href="http://www.scribd.com/doc/61105136/36/%C4%90%E1%BB%8Bnh-ngh%C4%A9a" class="toc_section_link" data-first-page="35" data-section="36">2.8.1.Định nghĩa :</a></li><li style="display: none;" class="toc_section toc_section_4 not_first_page" data-first-page="36" data-section="37"><a href="http://www.scribd.com/doc/61105136/37/%C6%AFu-%C4%91i%E1%BB%83m-c%E1%BB%A7a-h%E1%BB%87-th%E1%BB%91ng" class="toc_section_link" data-first-page="36" data-section="37">2.8.2.1.Ưu điểm của hệ thống</a></li><li style="display: none;" class="toc_section toc_section_4 not_first_page" data-first-page="36" data-section="38"><a href="http://www.scribd.com/doc/61105136/38/Nh%E1%BB%AFng-%C4%91i%E1%BB%83m-con-h%E1%BA%A1n-ch%E1%BA%BF-c%E1%BB%A7a-h%E1%BB%87-th%E1%BB%91ng" class="toc_section_link" data-first-page="36" data-section="38">2.8.2.2.Những điểm còn hạn chế của hệ thống</a></li><li style="display: none;" class="toc_section toc_section_4 not_first_page" data-first-page="37" data-section="39"><a href="http://www.scribd.com/doc/61105136/39/Ngon-ng%E1%BB%AF-l%E1%BA%ADp-trinh" class="toc_section_link" data-first-page="37" data-section="39">3.1.Ngôn ngữ lập trình</a></li><li style="display: none;" class="toc_section toc_section_5 not_first_page" data-first-page="37" data-section="40"><a href="http://www.scribd.com/doc/61105136/40/Th%C6%B0-vi%E1%BB%87n-s%E1%BB%91-nguyen-l%E1%BB%9Bn" class="toc_section_link" data-first-page="37" data-section="40">3.2.Thư viện số nguyên lớn</a></li><li style="display: none;" class="toc_section toc_section_5 not_first_page" data-first-page="37" data-section="41"><a href="http://www.scribd.com/doc/61105136/41/C%E1%BA%A5p-phat" class="toc_section_link" data-first-page="37" data-section="41">3.3.1.Cấp phát</a></li><li style="display: none;" class="toc_section toc_section_5 not_first_page" data-first-page="49" data-section="42"><a href="http://www.scribd.com/doc/61105136/42/Ch%E1%BB%A9ng-th%E1%BB%B1c" class="toc_section_link" data-first-page="49" data-section="42">3.3.2.Chứng thực</a></li><li style="display: none;" class="toc_section toc_section_5 not_first_page" data-first-page="50" data-section="43"><a href="http://www.scribd.com/doc/61105136/43/Toan-v%E1%BA%B9n-d%E1%BB%AF-li%E1%BB%87u" class="toc_section_link" data-first-page="50" data-section="43">3.3.3.Toàn vẹn dữ liệu</a></li><li style="display: none;" class="toc_section toc_section_5 not_first_page" data-first-page="51" data-section="44"><a href="http://www.scribd.com/doc/61105136/44/Thu-h%E1%BB%93i" class="toc_section_link" data-first-page="51" data-section="44">3.3.4.1.Thu hồi</a></li><li style="display: none;" class="toc_section toc_section_5 not_first_page" data-first-page="54" data-section="45"><a href="http://www.scribd.com/doc/61105136/45/C%E1%BA%A5p-phat-l%E1%BA%A1i" class="toc_section_link" data-first-page="54" data-section="45">3.3.4.2.Cấp phát lại</a></li></ul></div><script>$$('#sectionlist li.not_first_page').each(function(el){el.hide()});</script></div><div id="exposed_share_panel"><h3>Share &amp; Embed</h3><div class="share_button_container"><a class="fb_btn " href="http://www.facebook.com/sharer.php?u=http%3A%2F%2Fwww.scribd.com%2Fdoc%2F61105136%2FTran-Quang-Thuan-K51MMT-Khoa-Luan-Tot-Nghiep-Dai-Hoc%23source%3Afacebook" rel="nofollow"></a><a class="twtr_btn " 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<option value="241">Maps</option>
<option value="231">Origami</option>
<option value="234">Photography</option>
<option value="233">Posters</option></select>
			  
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			  <div class="child_54_container upload_widget_category_menus_subcontainer" style="display:none">
			  
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<option value="239">Literature</option>
<option value="55">Math &amp; Engineering</option>
<option value="65">Science</option></select>
			  
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